| Noun | 1. | cecum - the cavity in which the large intestine begins and into which the ileum opens; "the appendix is an offshoot of the cecum"large intestine - beginning with the cecum and ending with the rectum; includes the cecum and the colon and the rectum; extracts moisture from food residues which are later excreted as feces cecal appendage, vermiform appendix, vermiform process, appendix - a vestigial process that extends from the lower end of the cecum and that resembles a small pouch |