Definition of "plethory"

[T]he appetite falls down like a horseleech, when it is ready to burst with putrefaction and an unwholesome plethory […] .

1651, Jer[emy] Taylor, “[XXVIII Sermons Preached at Golden Grove; Being for the Summer Half-year, […].] ”, in ΕΝΙΑΥΤΟΣ [Eniautos]. A Course of Sermons for All the Sundays of the Year. […], 2nd edition, London: […] Richard Royston […], published 1654

The disease of the state is a plethory, / Who so fit to reduce it as I?

1820, Percy Bysshe Shelley, Oedipus Tyrannus

‘It is, indeed, owing to a plethory of matter that his style is so faulty.’

1791, James Boswell, Life of Johnson, Oxford, published 2008, page 921