It’s “wingdings” with a “g” in the name!\definefontsynonym[Wingdings][file:wingdings]\def\WingdingsSymbol{\getglyphdirect{Wingdings}}
\definesymbol[smiley:1][\WingdingsSymbol{74}]\definesymbol[smiley:2][\WingdingsSymbol{75}]\definesymbol[smiley:3][\WingdingsSymbol{76}]\starttext\symbol[smiley:1] \symbol[smiley:2] \symbol[smiley:3]\stoptext