1 arrogance; presumptuous behaviour.
2 a the act of presuming a thing to be true. b a thing that is or may be presumed to be true.
3 a ground for presuming (a strong presumption against their being guilty).
4 Law an inference from known facts.
Etymology: ME f. OF presumpcion f. L praesumptio -onis (as PRESUME)
Useful english dictionary. 2012.