1. (Scandanavian folklore) a supernatural creature (either a dwarf or a giant) that is supposed to live in caves or in the mountains
2. a partsong in which voices follow each other; one voice starts and others join in one after another until all are singing different parts of the song at the same time;
"they enjoyed singing rounds"
3. a fisherman's lure that is used in trolling;
"he used a spinner as his troll"
4. angling by drawing a baited line through the water