Real Dictionary

firm
A firm decision or opinion is definite and unlikely to change.
adjective: If someone's grip is firm or if they perform a physical action in a firm way, they do it with quite a lot of force or pressure but also in a controlled way.
adjective: If something is firm, it does not change much in shape when it is pressed but is not completely hard.
adjective: If something is firm, it does not shake or move when you put weight or pressure on it, because it is strongly made or securely fastened.
adjective: If you describe someone as firm, you mean they behave in a way that shows that they are not going to change their mind, or that they are the person who is in control.
countable noun: A firm is an organization which sells or produces something or which provides a service which people pay for.

firm in American English 1
not yielding easily under pressure; solid; hard
adjective: not soft or yielding when pressed; comparatively solid, hard, stiff, or rigid
adverb: firmly
intransitive verb: to become firm or fixed
transitive verb: to make firm; tighten or strengthen

firm in American English 2
a business company or partnership of two or more persons
noun: a partnership or association for carrying on a business

firm in British English 1
adjective: not soft or yielding to a touch or pressure; rigid; solid
adverb: in a secure, stable, or unyielding manner
verb: to make or become firm

firm in British English 2
noun: a business partnership