to attack vigorously or violently; assault.

to attack with arguments, criticism, ridicule, abuse, etc.

to assail one's opponent with slander.

to undertake with the purpose of mastering

He assailed his studies with new determination.

to impinge upon; make an impact on; beset

His mind was assailed by conflicting arguments. The light assailed their eyes.

adjective

safe , guarded , protected , secure

adjective

vulnerable , defenseless , exposed , weak , conquerable , in danger , undefendable , attackable , pregnable , vincible