The Collaborative International Dictionary of English v.0.48:

Pickeer \Pick*eer"\, v. i. [imp. & p. p. Pickeered; p. pr. &
   vb. n. Pickeering.] [F. picorer to go marauding, orig., to
   go to steal cattle, ultimately fr. L. pecus, pecoris, cattle;
   cf. F. picor['e]e, Sp. pecorea robbery committed by
   straggling soldiers.]
   To make a raid for booty; to maraud; also, to skirmish in
   advance of an army. See Picaroon. [Obs.] --Bp. Burnet.
   [1913 Webster]