in (also †of) one piece: consisting of a single element, part or body; undivided, uniform; (figurative) unharmed, undamaged, intact.

Phrases with prepositions, belonging to the preceding senses. at a lump: in one mass; in a single piece or quantity.

of a piece: (a) consisting of a single part, mass, or body; (b) of one and the same kind or quality; uniform, consistent, in accordance.

Phrases with prepositions, belonging to the preceding senses. in a lump: the whole together; all at once.

Phrases with prepositions, belonging to the preceding senses. all of a lump: altogether, in a heap; also, swollen so as to appear one lump.