The Collaborative International Dictionary of English v.0.48:
Smooth-tongued \Smooth"-tongued`\, a. Having a smooth tongue; plausible; flattering. [1913 Webster]WordNet (r) 3.0 (2006):
smooth-tongued adj 1: artfully persuasive in speech; "a glib tongue"; "a smooth-tongued hypocrite" [syn: glib, glib-tongued, smooth-tongued]