The word(s) "guess" appears 7 time(s) in 6 verse(s) in Quran in Mohsin Khan translation.

(1) And there are among them (Jews) unlettered people, who know not the Book, but they trust upon false desires and they but guess.

(2) Those who took partners (in worship) with Allah will say: "If Allah had willed, we would not have taken partners (in worship) with Him, nor would our fathers, and we would not have forbidden anything (against His Will)." Likewise belied those who were before them, (they argued falsely with Allah's Messengers), till they tasted Our Wrath. Say: "Have you any knowledge (proof) that you can produce before us? Verily, you follow nothing but guess and you do nothing but lie."

(3) (Some) say they were three, the dog being the fourth among them; and (others) say they were five, the dog being the sixth, - guessing at the unseen; (yet others) say they were seven, and the dog being the eighth. Say (O Muhammad صلى الله عليه وسلم): "My Lord knows best their number; none knows them but a few." So debate not (about their number) except with the clear proof (which We have revealed to you). And consult not any of them (people of the Scripture - Jews and Christians) about (the affair of) the people of the Cave.

(4) [Dawud (David)] said (immediately without listening to the opponent): "He has wronged you in demanding your ewe in addition to his ewes. And, verily, many partners oppress one another, except those who believe and do righteous good deeds, and they are few." And Dawud (David) guessed that We have tried him and he sought Forgiveness of his Lord, and he fell down prostrate and turned (to Allah) in repentance.

(5) They are but names which you have named - you and your fathers - for which Allah has sent down no authority. They follow but a guess and that which they themselves desire, whereas there has surely come to them the Guidance from their Lord!

(6) But they have no knowledge thereof. They follow but a guess, and verily, guess is no substitute for the truth.