From WordNet (r) 3.0 (2006) :
unfastened
adj 1: not closed or secured; "the car door was unfastened";
"unfastened seatbelts" [ant: fastened]
2: affording unobstructed entrance and exit; not shut or closed;
"an open door"; "they left the door open" [syn: open,
unfastened] [ant: closed, shut, unopen]
3: not buttoned; "the wind picked up the hem of her unbuttoned
coat" [syn: unbuttoned, unfastened] [ant: buttoned,
fastened]
4: not tied [syn: untied, unfastened] [ant: fastened,
tied]