If something is firm, it does not change much in shape when it is pressed but is not completely hard.

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.

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.

A firm decision or opinion is definite and unlikely to change.

Firm evidence or information is based on facts and so is likely to be true.

You use firm to describe control or a basis or position when it is strong and unlikely to be ended or removed.

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.

A firm is an organization which sells or produces something or which provides a service which people pay for.

If you firm up something or if it firms up, it becomes firmer and more solid.

If you firm something up or if it firms up, it becomes clearer, stronger, or more definite.

If someone stands firm, they refuse to change their mind about something.