micropyle UK /ˈmaɪ.kɹəʊˌpaɪl/US /ˈmaɪ.kɹoʊˌpaɪl/ noun2 •In seed-bearing plants, a small opening in the integuments of the ovule through which sperm are able to access the ovum. •The hilum of an ovum at the point of attachment to the ovary; any opening in the coverings of an ovum by which spermatozoa may find entrance. formsmicropyles