Objection 1. It would seem that reviling does not consist in words. Reviling implies some injury inflicted on one's neighbor, since it is a kind of injustice. But words seem to inflict no injury on one's neighbor, either in his person, or in his belongings. Therefore reviling does not consist in words.
Objection 2. Further, reviling seems to imply dishonor. But a man can be dishonored or slighted by deeds more than by words. Therefore it seems that reviling consists, not in words but in deeds.
Objection 3. Further, a dishonor inflicted by words is called a railing or a taunt. But reviling seems to differ from railing or taunt. Therefore reviling does not consist in words.
On the contrary, Nothing, save words, is perceived by the hearing. Now reviling is perceived by the hearing according to Jeremiah 20:10, "I heard reviling [Douay: 'contumelies'] on every side." Therefore reviling consists in words.
I answer that, Reviling denotes the dishonoring of a person, and this happens in two ways: for since honor results from excellence, one person dishonors another, first, by depriving him of the excellence for which he is honored. This is done by sins of deed, whereof we have spoken above (64, seqq.). Secondly, when a man publishes something against another's honor, thus bringing it to the knowledge of the latter and of other men. This reviling properly so called, and is done I some kind of signs. Now, according to Augustine (De Doctr. Christ. ii, 3), "compared with words all other signs are very few, for words have obtained the chief place among men for the purpose of expressing whatever the mind conceives." Hence reviling, properly speaking consists in words: wherefore, Isidore says (Etym. x) that a reviler [contumeliosus] "is hasty and bursts out [tumet] in injurious words." Since, however, things are also signified by deeds, which on this account have the same significance as words, it follows that reviling in a wider sense extends also to deeds. Wherefore a gloss on Romans 1:30, "contumelious, proud," says: "The contumelious are those who by word or deed revile and shame others."
Reply to Objection 1. Our words, if we consider them in their essence, i.e. as audible sound injure no man, except perhaps by jarring of the ear, as when a person speaks too loud. But, considered as signs conveying something to the knowledge of others, they may do many kinds of harm. Such is the harm done to a man to the detriment of his honor, or of the respect due to him from others. Hence the reviling is greater if one man reproach another in the presence of many: and yet there may still be reviling if he reproach him by himself. in so far as the speaker acts unjustly against the respect due to the hearer.
Reply to Objection 2. One man slights another by deeds in so far as such deeds cause or signify that which is against that other man's honor. On the former case it is not a matter of reviling but of some other kind of injustice, of which we have spoken above (Q64,65,66): where as in the latter case there is reviling, in so far as deeds have the significant force of words.
Reply to Objection 3. Railing and taunts consist in words, even as reviling, because by all of them a man's faults are exposed to the detriment of his honor. Such faults are of three kinds. First, there is the fault of guilt, which is exposed by "reviling" words. Secondly, there is the fault of both guilt and punishment, which is exposed by "taunts" [convicium], because "vice" is commonly spoken of in connection with not only the soul but also the body. Hence if one man says spitefully to another that he is blind, he taunts but does not revile him: whereas if one man calls another a thief, he not only taunts but also reviles him. Thirdly, a man reproaches another for his inferiority or indigence, so as to lessen the honor due to him for any kind of excellence. This is done by "upbraiding" words, and properly speaking, occurs when one spitefully reminds a man that one has succored him when he was in need. Hence it is written (Sirach 20:15): "He will give a few things and upbraid much." Nevertheless these terms are sometimes employed one for the other.
Source: Summa Theologica (New Advent)