What is the meaning of the word "firm"?

Definitions:

become taut or tauter verb
- Your muscles will firm when you exercise regularly
not liable to fluctuate or especially to fall adjective
- stocks are still firm
not soft or yielding to pressure adjective
- a firm mattress
not subject to revision or change adjective
- a firm contract
of especially a person's physical features, not shaking or trembling adjective
- My voice is firm and confident.
possessing the tone and resiliency of healthy tissue adjective
- firm muscles
securely established adjective
- holds a firm position as the country's leading poet
securely fixed in place adjective
- the post was still firm after being hit by the car
strong and sure adjective
- a firm grasp
unwavering in devotion to friend or vow or cause adjective
- a firm ally
with resolute determination adverb
- we firmly believed it