slippery

Causing or tending to cause sliding or slipping.

Tending to slip, as from one's grasp.

Not trustworthy; elusive or tricky.

Having such smoothness of surface as to cause slipping or sliding, or to render grip or hold difficult; not affording firm footing or secure hold.

Hence That cannot be depended on or trusted; uncertain; untrustworthy; apt to play one false; dishonest.