Chalky means like chalk, or with chalk in it: dry, pale, and a little powdery. A cliff can be chalky when the rock itself is chalk. Soil can be chalky too — pale, and not much good for some plants. A taste is chalky when it sits on your tongue like dust, the way some cheap chocolate, tablets, or dry biscuits do; there may be no real chalk in them at all. Skin looks chalky when it is very white, or when powder is sitting on it. Paint or make-up is chalky when the colour is flat and dusty, not fresh and bright. People stretch it a little for anything that feels dry and white in that same way. It is an ordinary describing word, not slang and not fancy.