The last meaning is the one most often used.
enceinte
n.
5Fr < pp. of enceindre < L incingere, to gird about < in, in + cingere, to surround6
1 the line of works enclosing a fortified place
2 the space so enclosed

en[ceinte 79n sant$; E en sant$8
adj.
5Fr < ML incincta, orig. fem. of incinctus, ungirt < L in3, not + cinctus, pp. of cingere, to gird, surround: see CINCH6 pregnant; with child