From WordNet (r) 3.0 (2006) [wn]:
presumably
adv 1: by reasonable assumption; "presumably, he missed the
train" [syn: presumably, presumptively]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Presumably \Pre*sum"a*bly\, adv.
In a presumable manner; by, or according to, presumption.
[1913 Webster]