The Collaborative International Dictionary of English v.0.48:

Neoplasm \Ne"o*plasm\ (n[=e]"[-o]*pl[a^]z'm), n. [See
   Neoplasia.] (Physiol. & Med.)
   A new formation or tissue, the product of morbid action.
   [1913 Webster]

WordNet (r) 3.0 (2006):

neoplasm
    n 1: an abnormal new mass of tissue that serves no purpose [syn:
         tumor, tumour, neoplasm]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "neoplasm":
   benign tumor, callosity, callus, cancer, carcinoma, corn, cyst,
   excrescence, fungosity, fungus, growth, intumescence,
   malignant growth, metastatic tumor, mole, morbid growth, nevus,
   nonmalignant tumor, outgrowth, proud flesh, sarcoma, tumor,
   verruca, wart, wen