Definition of "peaky"

Her appetite did not improve, however, and she looked very thin and peaky.

1956 , Johanna Spyri, translated by Eileen Hall, Heidi, page 111

Or over hills with peaky tops engrail'd, / And many a tract of palm and rice, / The throne of Indian Cama slowly sail'd / A summer fann'd with spice.

1842, Alfred Tennyson, “The Palace of Art”, in Poems. […], volume I, London: Edward Moxon, […], page 143

A wide spread of possible outcomes will give a relatively flat distribution and so indicate a risky project. A narrow spread of results will give a very peaky graph and indicate a low risk project.

1994, John S. Hares, Duncan Royle, Measuring the value of information technology, page 176