The Collaborative International Dictionary of English v.0.48:

Maverick \Mav"er*ick\, v. t.
   To take a maverick. [Western U. S.]
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Maverick \Mav"er*ick\, n.
   In the southwestern part of the united States, a bullock or
   heifer that has not been branded, and is unclaimed or wild;
   -- said to be from Maverick, the name of a cattle owner in
   Texas who neglected to brand his cattle.
   [1913 Webster]

WordNet (r) 3.0 (2006):

maverick
    adj 1: independent in behavior or thought; "she led a somewhat
           irregular private life"; "maverick politicians" [syn:
           irregular, maverick, unorthodox]
    n 1: someone who exhibits great independence in thought and
         action [syn: maverick, rebel]
    2: an unbranded range animal (especially a stray calf); belongs
       to the first person who puts a brand on it