sur·mise 
(sər-mīz)
(sər-mīz)v. sur·mised, sur·mis·ing, sur·mis·es
v.tr.
1. To make a judgment about (something) without sufficient evidence; guess: "In another pocket he came across what he surmised in the dark were pennies, erroneously, however, as it turned out" (James Joyce).
2. To say (something) as a guess or conjecture.
v.intr.
To make a guess or conjecture.
n.
An idea or opinion based on insufficiently conclusive evidence; a conjecture.
[Middle English surmisen, to accuse, from Old French surmise, feminine past participle of surmettre : sur-, sur- + mettre, to put (from Latin mittere).]