formal repellent or unattractive
Still, everyone appeared to be extremely nice, except that that Dr. Greenfield man was a trifle rebarbative. (This was a word which Toby had recently learnt at school and could not now conceive of doing without.) — Iris Murdoch
[French rébarbatif from early French rebarber to be repellent, ultimately from Latin barba beard, from the notion of two people facing each other aggressively, beard to beard]