n. The name of the Greek letter Λ, λ (equivalent to the Roman L, l).n. In craniology, the junction of the sagittal and lambdoid sutures at the apex of the latter. See cut under craniometry.n. A British collectors' name for a common Old World noctuid moth, Plusia gamma, occurring in Europe, China, Japan, and India, and also, probably by introduction, in South America.