(grammar, X-bar theory) A phrase, or, equivalently, a node in a syntax tree, which consists either of: (1) an adjunct and another X-bar phrase, (2) a head, X, and an optional complement, or (3) a conjunction sandwiched between two other X-bars. The X is a "pro-letter" which can be substituted by letters such as N for noun, V for verb, P for preposition, I for inflectional, etc.

(genetics) Associated with the X chromosome.

Unix-like operating system (e.g., Linux, macOS, Solaris, etc.).

The theory that employees are inherently lazy and irresponsible and will tend to avoid work unless closely supervised and given incentives.

plural of x-ray

(informal, usually used attributively) cross-country / (informal) cross-country skiing

Across the country.

plural of X-junction

A symbol composed of two perpendicular lines (✗), especially when representing negation or lack of verification.

plural of X mark