In a complex multilingual state such as Nigeria, the need to ease social intercourse often arises and may result in linguistic creativity/productivity. One of such products is ample slang usage. This paper reports the outcome of a study which investigated an inventory of Nigerian slangs; their lexical and semantic structure, word formation processes involved in production, their function, context of use and meaning. An Inventory of a hundred and twenty colloquial and vocational slangs was sampled. The corpus was gathered by using questionnaire drawn to provide slangs (from institution of higher learning) along with their meaning in areas related to food, clothes, persons, mannerism, relationships, Infrastructures, and socialization. Interviews and participatory/obtrusive observation methods were also employed via recorded conversation; to identify the context of meaning. Findings confirm youth population as a major source. Borrowing, Acronym, Reduplication, Compounding, Blending, Clipping, and Conversion were the main processes of word formation employed; to yield a range of semantic possibilities. Their effects in further enriching existing languages, on language standardization, language birth and death, as well as their additional usefulness as illustrative material for lexicology are further examined.