Off-puttingly is the -ly form of off-putting. If someone behaves off-puttingly, or a room is off-puttingly dark, the way they act or the way it looks makes you not want to come closer — you do not like it, or you find it unattractive. Same idea as off-putting, just used with a verb or before another describing word. Though actually, it is a long, slightly stiff way to say it; many people just say “in an off-putting way,” or they use the adjective and stop there. Students need off-putting far more often than this adverb.