collīsĭo (conl-), ōnis, f. [collido],
I a dashing or striking together , a concussion , shock : partūs abjecti, Just. 11, 12, 6.—
II Transf., of letters in a word: πνεῖν, χεῖν, ῥεῖν, non sunt integra, sed ex collisione contracta. Macr. Diff. 19, § 17.