Frombreast +‎-less.

breastless (notcomparable)

1. Without abreast or breasts;flat-chested.
   • 1920,T. S. Eliot, “Whispers of Immortality”, inCollected Poems, 1909-1962, New York: Harcourt, Brace & World, published1963, page45:

     Webster was much possessed by death / And saw the skull beneath the skin; / Andbreastless creatures under ground / Leaned backward with a lipless grin.

   • 1925,Virginia Woolf,Mrs Dalloway, Penguin, published1992:

     […] she paused by the open staircase window which let in blinds flapping, dogs barking, let in, she thought, feeling herself suddenly shrivelled, aged,breastless, the grinding, blowing, flowering of the day, out of doors, out of the window, out of her body and brain which now failed[…]

   • 1934,George Orwell, chapter 8, inBurmese Days‎^[1]:

     A girl who had been squatting at the back of the stage, smoking, stepped forward into the lamplight. She was very young, slim-shouldered,breastless[…]

• breastlessness

• stressable