The Collaborative International Dictionary of English v.0.48:

Atrip \A*trip"\, adv. [Pref. a- + trip.] (Naut.)
      (a) Just hove clear of the ground; -- said of the anchor.
      (b) Sheeted home, hoisted taut up and ready for trimming;
          -- said of sails.
      (c) Hoisted up and ready to be swayed across; -- said of
          yards.
          [1913 Webster]

WordNet (r) 3.0 (2006):

atrip
    adj 1: (of an anchor) just clear of the bottom [syn: aweigh,
           atrip]