Polysemy‏ [Noun.]

‘When we encounter two or more words with the same form and related meanings, we have what is technically known as polysemy. Polysemy can be defined as one form (written or spoken) having multiple meanings that are all related by extension. Examples are the word head, used to refer to the object on top of your body, froth on top of a glass of beer, person at the top of a company or department, and many other things.’

– Yule, G. 1985. The Study of Language Cambridge, United Kingdom: Cambridge University Press (2010) p. 120