The Collaborative International Dictionary of English v.0.48:
layby \layby\ n. A paved area beside a main road where cars can stop temporarily. [Chiefly Brit.] Syn: pull-off, turnout. [WordNet 1.5]WordNet (r) 3.0 (2006):
layby n 1: designated paved area beside a main road where cars can stop temporarily [syn: pull-off, rest area, rest stop, layby, lay-by]