The word "un sleeping" is actually two words that have been combined to create a new word. The first word "un" is a prefix that means "not" or "opposite of". The second word "sleeping" is the present participle form of the verb "sleep". The vowel sound of "un" is pronounced as /ʌn/ and the syllable stress is on the first syllable. When combined, the pronunciation is /ʌnˈsliːpɪŋ/ with the stress on the second syllable. Therefore, "un sleeping" means not sleeping or awake.