Defensibling (dĭ-fĕn-sĭb’lĭng) Function: Noun 1. A celebrity’s lesser-known, fame-seeking sibling who becomes embarrassingly defensive at the very mention of his/her world-famous sister or brother. See also : Above video of Solange Knowles on Fox News Las Vegas , in which she mistakenly thought they’d introduced her along with a mention of Beyonce and ...