A Kansai dialect word meaning 'truth' or 'really'. Used conversationally to mean 'truly' or 'it's true'. Usually written in kana.
それはほんまなん？
Is that for real?
ほんまやで、彼は昨日来なかった。
It's true — he didn't come yesterday.
君のことをほんまに信じてる。
I truly believe in you.
あの店のラーメンはほんまにおいしい。
That shop's ramen is really tasty.