noun Etymology: Late Latin, literally, third something; from its failing to fit into a dichotomy Date: circa 1724 a middle course or an intermediate component , a third party of ambiguous status
TERTIUM QUID
Meaning of TERTIUM QUID in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012