picket

Concise Oxford English Dictionary © 2008 Oxford University Press:
picket/ˈpɪkɪt/

▶noun

• 1 a person or group of people standing outside a workplace trying to persuade others not to enter during a strike.

• 2 (also picquet or piquet) a soldier or small body of troops sent out to watch for the enemy.

• 3 [usu. as modifier] a pointed wooden stake driven into the ground to form a fence or to tether a horse.

▶verb (pickets, picketing, picketed) act as a picket outside (a workplace).

– derivatives
picketer noun.

– origin C17 (denoting a pointed stake, on which a soldier was required to stand on one foot as a military punishment): from Fr. piquet ‘pointed stake’.