Tilde (?), n. [Sp., fr. L. titulus a superscription, title, token, sign. See Title, n.] The accentual mark placed over n, and sometimes over l, in Spanish words [thus, ñ, <ilde_;], indicating that, in pronunciation, the sound of the following vowel is to be preceded by that of the initial, or consonantal, y.
[1913 Webster]