资料来源 : Webster's Revised Unabridged Dictionary (1913)

Unlash \Un*lash"\, v. t. [1st un- + lash.] (Naut.)
   To loose, as that which is lashed or tied down.

资料来源 : WordNet®

unlash
     v : untie the lashing of; "unlash the horse" [ant: {lash}]