tu·mor 
(tmər, ty-)
(tmər, ty-)n.
1. An abnormal growth of tissue resulting from uncontrolled, progressive multiplication of cells and serving no physiological function; a neoplasm.
2. A swollen part; a swelling: a plant tumor.
[Middle English tumour, from Latin tumor, from tumēre, to swell; see teuə- in the Appendix of Indo-European roots.]
tumor·al, tumor·ous adj.