D defs.my
Entry 1 sense Webster, 1913

Lessener

/(-ẽr)/ · Less·en·er · IPA
01 n. One who, or that which, lessens.
  1. 1.
    One who, or that which, lessens.
    “His wife . . . is the lessener of his pain, and the augmenter of his pleasure.” — J. Rogers (1839).