Rudimentary/ˌruːdɪˈmentri/ Definition 1 of 4Pro Tip 1/2Foundation Level Use 'rudimentary' to express something is at its most basic or beginning stage. She has a rudimentary understanding of physics. Pro Tip 2/2Not Complex 'Rudimentary' suggests lack of complexity, sophistication, or advanced features. The hotel offered only rudimentary accommodations.