Fowl and foul are homophones: same sound, but they have different meanings and spellings.
Fowl is a domestic cock or hen. Fowl is both a singular and plural noun, in addition to the plural noun: fowls. Example:
In some households in the villages, fowls and other domestic animals are kept especially in the countries of the Southern Hemisphere.
Fowl is the flesh of certain types of birds eaten for food. Example:
The Jogis had meat for the first course, roast fowl for the second course and vegetables for the third course for their dinner, which they celebrated for their family member’s birthday.
An archaic meaning of fowl is ‘any bird’. Example: Have you ever seen fowls of the air?
Fowl in compound nouns indicate the bird of the type specified such as waterfowls, barnyard fowls, wildfowls, peafowls, jungle fowls, and wildfowls.
Fowl as a verb refers to ‘hunt’ or ‘snare’ wildfowl. Example: It is not uncommon for some in the villages closer to forest areas go fowling.
Fowl pest is a type of infectious disease among chickens and other birds.
Fowl-Filcher is the title of the novel written by Ranga Rao. Fowl-Filcher is the story of the eponymous title (the fowl-filcher) is set in a hamlet surrounded by a jungle. Professor Ranga Rao taught at the Venkateswara College, University of Delhi.
‘Rao’s Fowl-Filcher bristled with rollicking laughter and it offered amusement at all levels – a full throated humour formed the format of the book.”- R. P. Chaddah, The Tribune.
Fowl-Filcher is a broad novel of many of India’s changes in the first decades after independence, and is especially appealing in its focus on smaller locales (while, in also moving beyond just village life, not remaining entire provincial). Fowl-Filcher’s varied life makes for interesting material, and Rao handles many of the episodes quite well, but the novel lacks the coherence of a true continuum, jerking forward too often.” –M. A. Orthofer (in complete-review.com)
Foul has many meanings and functions as a noun, verb, and adjective. Please refer to a standard dictionary for its comprehensive meaning, derivatives, and usage.
Foul as adjective means having a bad smell, bad taste, something dirty and disgusting, unpleasant or dreadful; of language, obscene, offensive such as using sear-words; of weather, very rainy, windy, stormy, rough; in sport, an action against the rules that are unfair
Foul as a noun refers to an action in sport that is against the rules of a game. The foul by a member of the team costs dearly: losing the game.
Foul play is an unfair or illegal dealings in something, an action that is against the rules of a game, unfair.
Other forms of foul are foully (adverb), foulness (noun), foul-up (noun, informal, spoiling or upsetting of arrangements, relationships. Usage: Many projects foresee foul-ups). Idioms formed with foul are: by fair means or foul, fall foul of somebody or something.
Foul-mouthed is an adjective: foul-mouthed person is the one who uses obscene and offensive language.