A<unk> in chemistry usually is used to describe molecules or ensembles formed by the combination of ligands and metal ions.  Originally, a<unk> implied a reversible association of molecules, atoms, or ions through weak chemical bonds. As applied to coordination chemistry, this meaning has evolved.  Some metal<unk> s are formed virtually irreversibly and many are bound together by bonds that are quite strong.
Complex 
Diradical
Grief
Mosaic 
Meter
Outlier
Liquid
Cyclic compound