ex·per·i·ment·er \ ̷ ̷ˈ ̷ ̷ ̷ ̷ˌmentə(r)\noun orex·per·i·men·tor\“, (ˌ) ̷ ̷ˌ ̷ ̷ ̷ ̷ˈmen.ˌtȯ(ə)r, -ȯ(ə)\ (-s) : one that experiments or conducts an experiment; specifically: one that conducts an experiment in introspective psychology by arranging and determining the physical conditions of the observer's experience