Enter a clue or pattern or both:
The Clue
Particle named for a letter of the alphabet (4 letter answer)
The Answer
KAON
Tags
Notes
The answer KAON is so rare that it appears less than once every 2500 puzzles.
Related Clues
Unstable subatomic particle
Definition
KAON as a noun:
1. (kaon, kappa-meson, k-meson, K particle) = an unstable meson produced as the result of a high-energy particle collision