size¹ / sīz/ • n. 1. the relative extent of something; a thing's overall dimensions or magnitude; how big something is: the schools varied in size a forest the size of Connecticut| houses of all sizes. ∎  extensive dimensions or magnitude: she seemed slightly awed by the size of the building.2. each of the classes, typically numbered, into which garments or other articles are divided according to how large they are: I can never find anything in my size. ∎  a person or garment corresponding to such a numbered class: she's a size 10.• v. [tr.] alter or sort in terms of size or according to size: some drills are sized in millimeters. ∎  (size something up) estimate or measure something's dimensions: she was trying to size up a room with a tape measure. ∎  (size someone/something up) inf. form an estimate or rough judgment of someone or something: the two men sized each other up.• adj. [in comb.] having a specified size; sized: marble-size chunks of hail.PHRASES: of a size (of two or more people or things) having the same dimensions.of some size fairly large.that's about the size of it inf. said to confirm someone's assessment of a situation, esp. of one regarded as bad.to size to the dimensions wanted: the PVC sheet is easily cut to size.DERIVATIVES: siz·er n.size² • n. a gelatinous solution used in gilding paper, stiffening textiles, and preparing plastered walls for decoration.• v. [tr.] treat with size to glaze or stiffen.