From Longman Dictionary of Contemporary Englishtwo/three etc deeptwo/three etc deepLINEif things or people are two deep, three deep etc, there are two, three etc rows or layers of things or people People were standing four deep at the bar. → deep
Examples from the Corpus
two/three etc deep• As it was, I had to stand around a bar packed two and three deep.• I loved the first hour after the opening bell, when customers gathered three deep and the money poured in.• Alison Edwards suffered three deep cuts in her face when she accidentally fell through a shop window.• This had two deep leather armchairs, a big desk with a telephone on it, and books.• Two bulging boxes were stacked two deep on the right and left of the stage.• Best show ever-me light as a feather and them standing two deep on two levels!• A huge goat-hair sack would then be thrown over the saddle, forming two deep pockets either side. 