If you surmise that something is true, you guess it from the available evidence, although you do not know for certain. There's so little to go on, we can only surmise what happened He surmised that he had discovered one of the illegal streets
If you say that a particular conclusion is surmise, you mean that it is a guess based on the available evidence and you do not know for certain that it is true. It is mere surmise that Bosch had Brant's poem in mind when doing this painting His surmise proved correct. = conjecture. to guess that something is true, using the information you know already surmise that (past participle of surmetre , from supermettere , from mittere )