(chemistry) Any of a group of molecules or ions that have the same number of valence electrons and have chemical or physical similarities. For example, SH, NH2 and CH3 are isosteres of OH.

A tendency among some conservative Christians, especially in the USA, to seek influence or control over secular civil government through political action.

(botany) Belonging to the Cunoniaceae.

(vulgar) Initialism of fuck all. / (euphemistic) Initialism of Fanny Adams.