lasso /læsˈuː/noun 2verb 1forms 4phrases 1 noun2 •A long rope with a sliding loop on one end, generally used in ranching to catch cattle and horses.He managed to catch the runaway bull with a lasso.She threw the lasso skillfully around the post. •An image-editing function allowing the user to capture an irregularly-shaped object by drawing an approximate outline. verb1 •To catch with a lasso.He had to lasso the wild horse before it ran off. formslassoed · lassoing · lassoes · lassos Phrases with lasso lasso upTo lasso someone or something; to catch someone with a leash or rope.