noun
hunch
HUNCH/hˈʌntʃ/
A feeling or guess not based on clear evidence.
The man follows a hunch when choosing among the identical closed boxes.

Etymology
Hunch first named a push or thrust, then figuratively a hint—a “push” toward an answer. That intermediate sense developed into a presentiment or intuitive guess.
In context
I think in June that the chances that it came from the lab looked to me to be about 90%. This is already ridiculous. 90% sure based on what? A hunch?
More examples
- Acting on a hunch, Maya checks the back door.
- His hunch about the surprise party turns out to be right.
- It's only a hunch, so let's check the numbers.
Forms
hunch · hunches