HOW BIG [C, U] › how big or small something is: It's an area about the size of Oxford. The size of some of those trees is incredible (= they are very large). MEASURE [C] › one of the different measurements in which things, for example clothes, food containers, etc are made: a size 10 skirt What size shoes do you take? I usually buy the 1.5 litre size. → See also all shapes and sizes