Lipoamide is a trivial name for 6,8-dithiooctanoic amide. It is 6,8-dithiooctanoic acid's functional form where the carboxyl group is attached to protein (or any other amine) by an amide linkage (containing -NH2). Sometimes lipoamide is used to refer to protein bound lipoic acid, but this can be misleading as this is technically incorrect. Lipoyl-protein or lipoyl-domain are better terms to refer to protein bound lipoic acid.
There are no reported occurrences of free lipoamide in nature.