Noun disappointment has 2 senses
  1. disappointment, letdown - a feeling of dissatisfaction that results when your expectations are not realized; "his hopes were so high he was doomed to disappointment"
    --1 is a kind of dissatisfaction
    --1 has particulars: frustration, defeat
    Derived form: verb disappoint1
  2. disappointment, dashing hopes - an act (or failure to act) that disappoints someone
    --2 is a kind of failure
    Derived form: verb disappoint1