The word is rarely attested in other dictionaries, but the existence of the cognate noun brullure (cf. the commentary to usler1) suggests that it is probably genuine.
s.
1burning, scorching by heat or fire:
(
1212; MS: 1212-13
)(God preserved holy man in fiery furnace) Q'onc n'i parut nis usleure As frenges de sa vesteure
11071
usleure (1212)