The Collaborative International Dictionary of English v.0.48:
Surmise \Sur*mise"\, v. t. [imp. & p. p. Surmised; p. pr. &
vb. n. Surmising.]
To imagine without certain knowledge; to infer on slight
grounds; to suppose, conjecture, or suspect; to guess.
It wafted nearer yet, and then she knew
That what before she but surmised, was true. --Dryden.
This change was not wrought by altering the form or
position of the earth, as was surmised by a very
learned man, but by dissolving it. --Woodward.