expression, ichidan verb
swerve from the course; stray from the path
Used both literally for ships/vehicles and figuratively for plans or life paths.
船は嵐で針路を逸れた。
The ship swerved from its course due to the storm.
彼の人生は悪い仲間のせいで針路を逸
His life strayed from the right path because of bad company.