The Collaborative International Dictionary of English v.0.48:

Picket \Pick"et\, v. t. [imp. & p. p. Picketed; p. pr. & vb.
   n. Picketing.]
   1. To fortify with pointed stakes.
      [1913 Webster]

   2. To inclose or fence with pickets or pales.
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   3. To tether to, or as to, a picket; as, to picket a horse.
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   4. To guard, as a camp or road, by an outlying picket.
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   5. To torture by compelling to stand with one foot on a
      pointed stake. [Obs.]
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "picketing":
   beef, bitch, boycott, challenge, complaint, compunction,
   confinement, demonstration, demur, demurrer, dismemberment,
   estrapade, exception, expostulation, galleys, grievance,
   grievance committee, hard labor, howl, impalement, imprisonment,
   incarceration, indignation meeting, jailing, keelhauling, kick,
   march, martyrdom, nonviolent protest, objection, penal servitude,
   protest, protest demonstration, protestation, qualm, railriding,
   rally, remonstrance, remonstration, rock pile, scruple, sit-in,
   squawk, strappado, strike, tar-and-feathering, teach-in,
   the gantlet, torment, torture