(military) The areas between a weapon and its target in which the trajectory is not greater than the typical height of a human (about 1.8 meters)

(mathematics) The vector space generated by all the column vectors of a matrix

(mathematics, physics) A space in which a generalization of quantum mechanics is described in terms of a system with a finite number of degrees of freedom

That part of an electron tube in which electrons interact with a modulated field

(mathematics, physics) A coordinate system (or a frame of reference) defined with respect to the distant stars, whose relative positions do not change over reasonably long periods of time

(mathematics) Any Riemann space in which the metric tensors are constants throughout

(letterpress typography) A piece of metal type used to create the narrowest space. / (typography, US) The narrowest space appearing between letters and punctuation.

To type (or format) text without leaving a blank line between each line of text. / To type (or format) text with only one space between consecutive sentences.

A broad step between flights of a staircase. / (mathematics) Either of the two parts of three-dimensional space divided by a plane.

(mathematics) A Riemann space in which the contracted curvature tensor is proportional to the metric tensor