1. the presence of multiple fibromas. 2. the formation of a fibrous, tumor-like nodule arising from the deep fascia, with a tendency to local recurrence. aggressive fibromatosis desmoid tumor, particularly one that is extra-abdominal.fibromatosis gingi´vae, gingival fibromatosis noninflammatory fibrous hyperplasia of the gingiva manifested as a dense, diffuse, smooth or nodular overgrowth of the gingival tissues.. the presence of multiple fibromas. 2. the formation of a fibrous, tumor-like nodule arising from the deep fascia, with a tendency to local recurrence. aggressive fibromatosis desmoid tumor, particularly one that is extra-abdominal.