(1):

(v. t.) To attack with violence, or in a vehement and hostile manner; to assault; to molest; as, to assail a man with blows; to assail a city with artillery.

(2):

(v. t.) To attack morally, or with a view to produce changes in the feelings, character, conduct, existing usages, institutions; to attack by words, hostile influence, etc.; as, to assail one with appeals, arguments, abuse, ridicule, and the like.

(3):

(v. t.) To encounter or meet purposely with the view of mastering, as an obstacle, difficulty, or the like.