collīsĭo

I. a dashing or striking together, a concussion, shock: partūs abjecti, Just. 11, 12, 6.—

II. Transf., of letters in a word: πνεῖν, χεἰν, ῥεῖν, non sunt integra, sed ex collisione contracta. Macr. Diff. 19, § 17.