Definitions

1. adjective

having the highest or best level of physical fitness or ability to survive or thrive in a particular environment

“The fittest athletes in the competition were rewarded with a trophy.”

2. noun

the most suitable or best person or thing for a particular task or situation

“She was considered the fittest person for the job and was eventually hired.”

3. noun (biology)

the individual or species best adapted to its environment, often with a higher chance of survival or reproduction

“The fittest species in a particular ecosystem were more likely to thrive in the long term.”