Definition of "elusive"

elusive

/ɪˈl(j)uː.sɪv/

adjective
comparative more elusive, superlative most elusive
1. Evading capture, comprehension or remembrance.
  Quotations
  The temporary elusive goal / To reach the solace, to feed once more upon the synthetic reaper of loss / No matter the outcome, the cost
  2002, Meshuggah, Closed Eye Visuals
2. Difficult to make precise.
  Quotations
  A precise definition of diarrhea is elusive
  2010, Robbins & Cotran Pathologic Basis of Disease
  Charley chased the elusive idea through all the nooks and crannies of his drowning consciousness.
  1910, Jack London, chapter 6, in Lost Face‎, archived from the original on 14 April 2011
3. Rarely seen.
  Quotations
  While you're sniffing the trunks of the ponderosas to see if they're butterscotch, vanilla, strawberry, or the elusive chocolate variety, watch for Brown Creepers, an elusive variety of bird.
  2002, Scott Roederer, Birding: Rocky Mountain National Park, page 93