(Not to be confused with suptilic.)
Suptiliasexual, also known as suptili-ace, or suptilic asexual, is a term referring to someone who is purely asexual, not grey ace or elsewhere on the asexual spectrum. A suptiliasexual person has never, and will never feel sexual attraction. It is similar to omniasexual.
Suptiliasexual comes from the Brazilian assexual estrito(a/e) which means "strict asexual". In Brazil the word asexual is an umbrella term for the entire spectrum. Someone fully asexual would be assexual estrito(a/e). In English these people would usually just be called "asexual" however, the term suptiliasexual is useful for when differentiating between suptiliasexuals and ace-spec people.