Source : Webster's Revised Unabridged Dictionary (1913)

Abeam \A*beam"\, adv. [Pref. a- + beam.] (Naut.)
   On the beam, that is, on a line which forms a right angle
   with the ship's keel; opposite to the center of the ship's
   side.

Source : WordNet®

abeam
     adv : at right angles to the length of a ship or airplane