You need a newer dictionary - it's in the latest OED.
Still not in Collins, though, and that's the one I use at work, but I would accept it if a contributor used it in their copy - few readers would have trouble understanding the term in the appropriate context, and the alternative would be to render your sentence clunky and inelegant, which to my mind would be a far more grievous solecism (the kind of thing up with which I will not put).