not in accordance with custom or habitual practice
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
How to use uncustomary in a sentence
In France it is not uncustomary to commit suicide at this stage; in England we do much better, or much worse, as the case may be.Return of the Native | Thomas Hardy
Customs are made for customary circumstances, and customary characters: and his circumstances or his character may be uncustomary.On Liberty | John Stuart Mill
It shows how human nature can adapt itself to the most uncustomary things.War Letters of a Public-School Boy | Paul Jones.
To refuse it was as uncustomary and as rude as to refuse the Alaskan miner who offers a drink at a public bar.White Shadows in the South Seas | Frederick O'Brien
So true is it that unnatural generally means only uncustomary, and that everything which is usual appears natural.The Subjection of Women | John Stuart Mill