Synonyms for Trench (same or very similar meaning)
WordNet sense 1 (a long steep-sided depression in the ocean floor):
deep, oceanic abyssWordNet sense 2 (impinge or infringe upon):
encroach, entrench, impingeWordNet sense 3 (cut a trench in, as for drainage):
ditchFrom the ODE community, based on WordNetadd/edit