By A.E. Waite (1911), tarot card illustrations by Pamela Colman Smith (1911)
Misery, distress, indigence, adversity, calamity, disgrace, deception, ruin. It is a card in particular of unforeseen catastrophe.
Divinatory Meanings – Reversed
According to one account, the same in a lesser degree also oppression, imprisonment, tyranny.
Occult explanations attached to this card are meagre and mostly disconcerting. It is idle to indicate that it depicts min in all its aspects, because it bears this evidence on the surface. It is said further that it contains the first allusion to a material building, but I do not conceive that the Tower is more or less material than the pillars which we have met with in three previous cases. I see nothing to warrant Papus in supposing that it is literally the fall of Adam, but there is more in favour of his alternative–that it signifies the materialization of the spiritual word. The bibliographer Christian imagines that it is the downfall of the mind, seeking to penetrate the mystery of God. I agree rather with Grand Orient that it is the ruin of the House of We, when evil has prevailed therein, and above all that it is the rending of a House of Doctrine. I understand that the reference is, however, to a House of Falsehood. It illustrates also in the most comprehensive way the old truth that “except the Lord build the house, they labour in vain that build it.”
There is a sense in which the catastrophe is a reflection from the previous card, but not on the side of the symbolism which I have tried to indicate therein. It is more correctly a question of analogy; one is concerned with the fall into the material and animal state, while the other signifies destruction on the intellectual side. The Tower has been spoken of as the chastisement of pride and the intellect overwhelmed in the attempt to penetrate the Mystery of God; but in neither case do these explanations account for the two persons who are the living sufferers. The one is the literal word made void and the other its false interpretation. In yet a deeper sense, it may signify also the end of a dispensation, but there is no possibility here for the consideration of this involved question.
16. The Tower struck by Lightning. Its alternative titles are: Castle of Plutus, God’s House and the Tower of Babel. In the last case, the figures falling therefrom are held to be Nimrod and his minister. It is assuredly a card of confusion, and the design corresponds, broadly speaking, to any of the designations except Maison Dieu, unless we are to understand that the House of God has been abandoned and the veil of the temple rent. It is a little surprising that the device has not so far been allocated to the destruction Of Solomon’s Temple, when the lightning would symbolize the fire and sword with which that edifice was visited by the King of the Chaldees.
By S. L. MacGregor Mathers, c 1888
The Lightning-struck Tower – Ruin, Disruption, Over-throw, Loss, Bankruptcy.
Divinatory Meanings – Reversed
These in a more or less partial degree.
Symbolism of the Keys
The Lightning-struck Tower – A Tower whose Upper part is like a crown, struck by a lightning-flash. (Two men fall headlong from it, One of whom is in such an attitude as to form a Hebrew letter Ayin.) Sparks and debris are falling. It shows Ruin, Disruption.
General Book of the Tarot
By A. E. Thierens, 
Description and Meaning
“Occult explanations attached to this card are meagre and mostly disconcerting.” (Waite) The reason for this is easily seen: the principles of Uranus and Neptune were not much known in antiquity save that they were the general principles of the Heavens (the Air or also the atmosphere) and the Ocean, and as such we find them in the Pantheon and in the original Tarot, not yet as the much later discovered planets, which personify these general cosmic principles. Later ages added very little, if anything at all, to those original explanations. Still Ouranos and Poseidon were known in Greece as well as Dourga and Varouna in India.
And the stone tower struck by a flash of lightning is another version of the legend of Ouranos mutilating his son Chronos, which means, that Heaven is not content with a body of fixed dimensions and form, nor any heavenly force with the limitations put to it by physical authorities or architects. This may warn man, not to build upon physical existence alone or to think himself safe upon a material basis, however high and solid it may appear from a material point of view. The general meaning, however, is not incidental but essential. “. . . the ruin of the house of life, when evil has prevailed therein” (Waite) is one of many possible occurrences; it may signify ‘blighted ambitions and hopes,’ etc. (Papus), but the universal and every day significance is: the renewal of the form, or rather of embodied life, by the force of Heaven, and of microcosm by the life of macrocosm, which incidentally of course breaks up forms here and there, if they are no longer fit for survival; the house of doctrine as well as every structure made by vanity, dogmatism and separativeness.
The Hebrew letter Ayin is addicted to this card. Papus utterly fails in giving any elucidation of this relationship. Waite has put it very clearly in this quotation: “Except the Lord build the house, they labour in vain that build it.”
So the card of the Tower signifies the relation between macro- and micro-cosm and will mean rupture, sudden disillusion, disenchantment, but also it symbolises intuition, renewal, help from above and clear insight in relation to vanity and sham projects, illusion and meaningless formalism.
By Paul Foster Case (1933)
16, Le Feu du Ciel
Corresponds, through the letter Peh, to Mars. The symbolism, which has, for a long time, been connected with the story of the Tower of Babel, has a direct bearing upon the divinatory meanings.
These meanings correspond also to the influence of Mars in astrology. As a rule an evil card, although in spiritual matters it may be understood as symbolizing the overthrow of mistaken conceptions, or the defeat of activities opposed to the Querant’s spiritual development. In material affairs it signifies ambition, unforeseen catastrophes, fighting, grave dangers, the ruin of the Querant’s plans, the defeat of his hopes.
More information on The Tower Tarot card.