1. Artfully persuasive in speech; SYN. glib-tongued, smooth-tongued.
2. Having only superficial plausibility; SYN. pat, slick.
3. Marked by lack of intellectual depth.

ETYM Latin speciosusgood-looking, beautiful, specious, from species look, show, appearance; cf. French spécoeux. Related to Species.
Plausible but false SYN. spurious.
Apparently good but not actually so; superficially plausible.
Plausible; superficial.

ETYM Latin spurius.
1. Not proceeding from the true source, or from the source pretended; not genuine; false; adulterated.
2. Not legitimate; bastard.