Synonyms for Deadening (same or very similar meaning)
WordNet sense 1 (so lacking in interest as to cause mental weariness):
boring, dull, ho-hum, irksome, slow, tedious, tiresome, wearisomeWordNet sense 2 (arousing no interest or attention or curiosity or excitement):
uninterestingWordNet sense 3 (the act of making something futile and useless (as by routine)):
constipation, impairment, stultificationFrom the ODE community, based on WordNetadd/edit