/hed"on", -awn"/ , adj.
1. (of two objects) meeting with the fronts or heads foremost: a head-on collision.
2. facing the direction of forward motion or alignment; frontal.
3. characterized by direct opposition: a head-on confrontation.
adv.
4. with the front or head foremost, esp. in a collision: She stepped out of the front door and walked head-on into her husband.
[ 1830-40, Amer. ]