adjective, sap·pi·er, sap·pi·est.
British Dictionary definitions for sappiest
adjective -pier or -piest
Word Origin and History for sappiest
"full of sap," Late Old English sæpig, from sæp (see sap (n.1)). Figurative sense of "foolishly sentimental" (1660s) may have developed from an intermediate sense of "wet, sodden" (late 15c.). Earlier, now obsolete, figurative senses were "full of vitality" (1550s) and "immature" (1620s).