glib 
(glĭb)
(glĭb)adj. glib·ber, glib·best
1. Performed with a natural, offhand ease: was fascinated by his unfailingly glib conversation.
2. Given to or characterized by fluency of speech or writing that often suggests insincerity, superficiality, or a lack of concern: criticized him for being glib about something so serious.
[Possibly of Low German origin; see ghel-2 in the Appendix of Indo-European roots.]
glibly adv.
glibness n.