tertium quid
/ˌtəːʃɪəm ˈkwɪd
/ /ˌtəːtɪəm /noun
A third thing that is indefinite and undefined but is related to two definite or known things.Unfortunately, given the interminability of the debate, only a few voices in the book seek to find a tertium quid - that is, a wider outlook that could lift the debate off its current hinges and onto a more illuminative level....
- Unable to fully reconcile the cases, Justice Scalia said that the trade dress in Two Pesos was either some form of packaging, or tertium quid.
Origin
Early 18th century: from late Latin, translation of Greek triton ti 'some third thing'.