ex·per·i·men·tal·ism \ikˌ ̷ ̷ ̷ ̷ˈmentəlˌizəm, (ˌ)ek-\noun (-s) 1. a.: a theory advocating experimental or empirical principles and procedures b.: pragmatist or instrumentalist theories, principles, and practices; specifically: those of John Dewey and his followers — compare instrumentalism, pragmatism 2.: the practice of relying on experiment