temperamental

Adjective

• likely to perform unpredictably; sometimes it would start and sometimes it wouldn't"
  • erratic winds are the bane of a sailor
    
  • a temperamental motor
    
  • that beautiful but temperamental instrument the flute- Osbert Lancaster
    

• subject to sharply varying moods
  • a temperamental opera singer
    

• relating to or caused by temperament
  • temperamental indifference to neatness
    
  • temperamental peculiarities
    

Related words

• Synonyms: 
  erratic , moody