maverick
1. [ noun ] someone who exhibits great independence in thought and action
Synonyms: rebel
Related terms: nonconformist rebel
2. [ adjective ] independent in behavior or thought
Synonyms: unorthodox irregular
Examples:

"she led a somewhat irregular private life" "maverick politicians"

Related terms: unconventional
3. [ noun ] (zoology) an unbranded range animal (especially a stray calf); belongs to the first person who puts a brand on it
Related terms: calf