From Longman Dictionary of Contemporary Englishunaccustomedun‧ac‧cus‧tomed /ˌʌnəˈkʌstəmd◂/ adjective formal 1 → unaccustomed to (doing) something2 [only before noun]UNUSUAL not usual, typical, or familiar She was completely exhausted by the unaccustomed heat.RegisterIn everyday English, people usually say that they are not used to something rather than unaccustomed to it:She wasn't used to living on her own.
Examples from the Corpus
unaccustomed• Extensive field research can mean long periods living under adverse conditions to which the researcher is unaccustomed.• Putting an economic rug back under the family means paying unaccustomed attention to issues of family business.• Imposing such a structure in baseball will take tough bargaining and unaccustomed discipline on the part of the owners.• Government service also brought Mr Packard unaccustomed public attention and made him and his company a magnet for controversy and protest.• As she stepped from her Rolls, Elinor shivered in the unaccustomed raw air of February.• unaccustomed speed and decisiveness• We became unaccustomed to silence, which was a signal for alarm.• They were people who were unaccustomed to silence, who were comforted by the racket of their own voices.• In fact she felt off her head, her mind a sickening unaccustomed whirl. 