All 5 Uses

supposition
in
Pride and Prejudice
(Edited)

They attacked him in various ways—with barefaced questions, ingenious suppositions, and distant surmises; but he eluded the skill of them all, and they were at last obliged to accept the second-hand intelligence of their neighbor, Lady Lucas.
p. 11.2

suppositions = guesses
She could only imagine, however, at last that she drew his notice because there was something more wrong and reprehensible, according to his ideas of right, than in any other person present. The supposition did not pain her. She liked him too little to care for his approbation.
p. 50.6 *

supposition = assumption or guess

editor's notes: Elizabeth misreads Darcy's attention as criticism when he's actually becoming attracted to her.
The hall, the dining-room, and all its furniture, were examined and praised; and his commendation of everything would have touched Mrs. Bennet's heart, but for the mortifying supposition of his viewing it all as his own future property.
p. 64.6

supposition = belief
The surprise of the rest of the family, on hearing who their visitor had been, was very great; but they obligingly satisfied it, with the same kind of supposition which had appeased Mrs. Bennet's curiosity; and Elizabeth was spared from much teasing on the subject.
p. 341.6

supposition = assumption
She followed him thither; and her curiosity to know what he had to tell her was heightened by the supposition of its being in some manner connected with the letter he held.
p. 341.8

supposition = expectation

Definitions:

(1) (supposition)
something supposed (rather than something known to be so) -- such as a disputed belief or assumption
(2) (meaning too rare to warrant focus)