directly; head-on; right in front
Describes facing something squarely, without avoidance; often used with verbs like 向き合う, 受ける, ぶつかる.
See also: まとも
He spoke looking me straight in the eye.
Implies taking something seriously, dealing with it honestly, or in a fair/decent manner; often used with verbs like 取り合う, 相手にする, 考える.
The typhoon hit this area head-on.
I can't speak properly because of a cold.
He can't do his job properly.
You shouldn't take his jokes seriously.
If you think about it seriously, you'll see that plan is impossible.
Adverbial form of the na-adjective まとも (proper, straight). The kanji 正面 are rarely used; the word is now almost always written in kana.