lengthening
1. [ adjective ] increasing in length
Examples:

"the lengthening days of February"

Related terms: increasing
2. [ noun ] the act of prolonging something
Synonyms: perpetuation prolongation protraction
Examples:

"there was an indefinite prolongation of the peace talks"

Related terms: continuance perpetuate prolong
Similar spelling:   lengthen
  lengthened
  lengthwise
  lengthiness
  lengthily