IPA: /ˌæntiˈhoʊməˌsɛkʃuəl/
KK: /æntiˈhoʊməˌsekʃuəl/
Opposed to or against homosexuality.
The legislation was criticized for its antihomosexual stance.
Antihomosexual is formed from "anti-" (meaning against) and "homosexual" (from Greek "homos" meaning same and "sexus" from Latin meaning sex). The word describes a stance or attitude that is against same-sex relationships or individuals.
Think of 'against' ('anti-') and 'same sex' ('homosexual') to remember that antihomosexual refers to being against same-sex relationships.