1. 
[syn: napping, off-guard(a), off guard(p), off one's guard(p), off his guard, off her guard, off your guard]
The Collaborative International Dictionary of English v.0.48:
off-guard \off-guard\ pred. adj.
   not watching for possible danger; not alert; as, caught in an
   off-guard moment.
   [WordNet 1.5]
WordNet (r) 3.0 (2006):
off-guard
    adj 1: not prepared or vigilant; "the blow caught him napping";
           "caught in an off-guard moment"; "found him off his
           guard" [syn: napping, off-guard(a), off guard(p),
           off one's guard(p), off his guard, off her guard,
           off your guard]