English definition of “firm”
NOT SOFT › not soft, but not completely hard: A firm bed is better for your back.
FIXED [always before noun] › certain or fixed and not likely to change: We don't have any firm plans for the weekend yet. I'm a firm believer in equal rights.
STRONG › strong and tight: a firm handshake/grip
STRICT › strict and making certain that people do what you want: You've got to be firm with children. firmly adverb firmness noun [U]