1: a musical ornament consisting of one or several short unaccented grace notes attached to and played in the time of the preceding main note or tone
2: the auxiliary closing note or notes usually played at the end of a trill
History and Etymology for nachschlag
German, literally, afterstroke, from Middle High German nāchslac blow struck from behind, from nāch after, behind (from Old High German nāh) + slac blow (from Old High German slag); akin to Old High German slahan to beat, strike