IPA: //ʌnˈsmaɪlɪŋ//
KK: /ʌnˈsmaɪlɪŋ/
Not showing a smile; having a serious or stern expression.
Despite the happy occasion, she remained unsmiling throughout the event.
Unsmiling → It is formed from "un-" (meaning not) and "smiling" (from Old English "smīlan", meaning to smile). The word "unsmiling" means not smiling or lacking a smile.
Think of 'not' ('un-') being added to 'smiling' — this helps you remember that 'unsmiling' means someone who is not smiling.