monocystPath.|ˈmɒnəsɪst| [f. mono- + cyst.] A tumour consisting of a single cyst. 1869T. G. Thomas Dis. Women (ed. 2) 553 The monocyst..develops the power of cysto-genesis and becomes poly-cystic.1897Allbutt's Syst.Med. II. 1110 The hydatid bladder..consists of a single simple sac or mono-cyst.