[count] 1 plural mediums : something that is sold in a medium size : something that is the middle size when compared with things that are larger and smaller ▪ I take a medium. ▪ These shirts are all mediums and I take a large. ▪ Make my French fries a medium.
2 plural usually media : a particular form or system of communication (such as newspapers, radio, or television) ▪ an effective advertising medium = an effective medium for advertising —see also media
3 : the materials or methods used by an artist ▪ Her preferred medium is sculpture. ▪ The artist works in two media/mediums, pencil and watercolor.
4 : the thing by which or through which something is done ▪ Money is a medium [=means] of exchange. ▪ English is an important medium of international communication.
5 plural mediums : a person who claims to be able to communicate with the spirits of dead people ▪ She visited a medium to try to talk to her dead son.
6 formal : a surrounding condition or environment ▪ Ocean fish live in a medium of salt water.