What it means

1. adjective indefinite in time or position
   “he will come one day”
2. adjective (informal) very
   “that is one fine dog”
3. adjective of the same kind or quality
   “two animals of one species”
4. adjective having the indivisible character of a unit
   “a unitary action”
5. adjective eminent beyond or above comparison
   “matchless beauty”