WordNet (r) 3.0 (2006):

cul de sac
    n 1: a passage with access only at one end [syn: cul, cul de
         sac, dead end]
    2: a street with only one way in or out [syn: blind alley,
       cul de sac, dead-end street, impasse]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

CUL DE SAC. This is a French phrase, which signifies, literally, the bottom
of a bag, and, figuratively, a street not open at both ends. It seems not to
be settled whether a cul de sac is to be considered a highway. See 1 Campb.
R. 260; 11 East, R. 376, note; 5 Taunt. R. 137; 5 B. & Ald. 456; Hawk. P. C.
b. 1, c. 76, s. 1 Dig. lib. 50, tit. 16, l. 43; Dig. lib. 43, t. 12, 1. Sec.
13; Dig. lib. 47, tit. 10, 1. 15, Sec. 7.