picketing       
noun [ U ] uk/ˈpɪk.ɪ.tɪŋ/ us/ˈpɪk.ɪ.t̬ɪŋ/
 纠察活动
an activity in which a worker or group of workers protest outside a building to prevent other workers from going inside
  The proposed new law would ban picketing. 拟议的新法将禁止纠察活动。 
 See: picket
 - More examples
 - The dramatic unfolding of events, particularly the mass picketing and the response of the police, is well known.
 - National NAACP leaders announced a boycott against the 24-hotel chain in July, calling for picketing outside hotels nationwide.
 - Ramp workers, who soundly rejected a contract deal and remain in mediated talks, this month staged the first picketing against the airline in more than two decades.