Answer: ppps

AnswerCrossword Clue
PPPSThird afterthought, in a ltr.
PPPSLong letter extender
PPPSMusical directions meaning "very soft."
PPPSPianissimo marks.
PPPSDirections in music.
PPPSThird addendum to a letter
PPPSThird afterthought in a letter: Abbr.
PPPSThird line at the bottom: Abbr.
PPPSThird afterthought in a missive: Abbr.
PPPSThought after an after-afterthought: Abbr.
PPPSThird afterthought abbr.