n. & adj.
n. esp. US 1 a flat or maisonette on two levels. 2 a house subdivided for two families.
adj. 1 having two elements; twofold. 2 esp. US a (of a flat) two-storeyed. b (of a house) for two families. 3 Computing (of a circuit) allowing the transmission of signals in both directions simultaneously (opp. SIMPLEX). half-duplex Computing (of a circuit) allowing the transmission of signals in both directions but not simultaneously.
[ L duplex duplicis f. duo two + plic- fold ]