An ELT Glossary : Skimming
Grellet (1981:19) gives the following definition of skimming :
When skimming, we go through the reading material quickly in order to get the gist of it, to know how it is organized, or to get an idea of the tone or the intention of the writer.
An example of skim reading might be looking through a newspaper. The reader would be likely to flick through the pages looking at the headlines and photos, and maybe quickly reading the opening paragraph of articles that look interesting. But only once s/he had decided that an article was definitely of interest or relevance would s/he start reading more intensively.
Skimming therefore contrasts with reading for detail, where the reader wishes to fully understand and retain the specific information that the text contains - for example, if you are reading an academic text and taking notes as you go.
Grellet, F. (1981) Developing Reading Skills, Cambridge : CUP