Bis \Bis\, adv. [L. bis twice, for duis, fr. root of duo two. See Two, and cf. Bi-.]

Twice; -- a word showing that something is, or is to be, repeated; as a passage of music, or an item in accounts.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Bis- \Bis-\, pref. A form of Bi-, sometimes used before s, c, or a vowel.

Source: Webster's Revised Unabridged Dictionary (1913)