A utility knife, usually with a short, sharp, disposable blade mounted on a pen-like body, usually for crafts and hobbies; an X-Acto knife.

(genetics) A non-linear strand of DNA where certain cruciform binding proteins can compete for binding.

tic-tac-toe / (idiomatic, sports) The fundamental elements of a play. / (idiomatic, management) The basic delineation of roles in a project.

Abbreviation of kisses and hugs.

present participle of X-ray

(astronomy) A hypothetical planet in the Solar system, beyond the currently known outermost planet. (The term was applied to Eris for a short while, when Pluto was still considered the ninth planet.)

simple past tense and past participle of X-ray

A SAMPA-inspired transcription of the International Phonetic Alphabet (IPA) into ASCII.

plural of X-chromosome

(algebraic geometry) The direction aligned with the x-axis of a coordinate system.