slippery Definition

1. So smooth, wet, etc as to cause or allow slipping.

Thesaurus: smooth, glazed, slick, sleek, oily, greasy, glassy, icy, wet; Antonym: rough, sticky.
2. Difficult to catch or keep hold of; elusive or evasive.
3. Unpredictable or untrustworthy.

Example: a slippery character
Thesaurus: devious, wily, capricious, elusive, double-talking, glib, slick, cunning, canny; Antonym: reliable.