if two vehicles crash etc head-on, the front part of one vehicle hits the front part of the other
if someone deals with a problem head-on, they do not try to avoid it, but deal with it in a direct and determined way
face/tackle/meet something head-on
The police are trying to tackle car crime head-on.
if two people or teams meet head-on in an argument, competition etc, they compete against each other and try to win in a very determined way