Used attributively before nouns, especially in technical contexts, to denote something relating to or characterized by a quirk.
Definitionen
Relating to or characteristic of legacy or non-standard behaviour, especially in web browsers ("quirk mode"). Older browsers may render the page in quirk mode, leading to inconsistent layouts.
Designating a narrow groove separating adjoining surfaces in moulding, joinery, or metalwork. The cabinetmaker applied a quirk moulding along the panel edges.