- Thine is defined as something belongs to you.
An example of thine is John telling Mary that the horse belongs to John, by saying the horse is thine.
thine definition by Webster's New World
Origin: Middle English thin ; from Old English genitive of thu, thou ( Middle English loss of -n before a consonant gives thy)
thine definition by American Heritage Dictionary
pron. (used with a sing. or pl. verb)
Origin: Middle English thin; see thy.