1. noun /læsˈuː,ˈlæs.oʊ,ˈlæs.u/
a) A long rope with a sliding loop on one end, generally used in ranching to catch cattle and horses.
b) An image-editing function allowing the user to capture an irregularly-shaped object by drawing an approximate outline.
2. verb /læsˈuː,ˈlæs.oʊ,ˈlæs.u/
To catch with a lasso.
Wikipedia foundation.