If you describe someone as oversexed, you mean that they are more interested in sex or more involved in sexual activities than you think they should be.
[disapproval]
oversexed in British English
(ˌəʊvəˈsɛkst)
adjective
having an excessive preoccupation with or need for sexual activity
oversexed in American English
(ˌoʊvərˈsɛkst; ˈoʊvərˌsɛkst)
adjective
characterized by an exceptional sexual drive or preoccupation with sexual matters