(1):
(a.) Not such as to inspire liking; unattractive; disagreeable.
(2):
(a.) Not likely; improbable; not to be reasonably expected; as, an unlikely event; the thing you mention is very unlikely.
(3):
(a.) Not holding out a prospect of success; likely to fail; unpromising; as, unlikely means.
(4):
(adv.) In an unlikely manner.