1. So lacking in interest as to cause mental weariness
   "a mind-numbing evening with uninteresting people";
   - boring, deadening, dull, ho-hum [informal], irksome, slow, tedious, tiresome, wearisome, unamusing, deadly [informal], draggy [informal]

See also: lame, lameo [informal], meh [informal], samey [Brit, informal], uninspiring, uninteresting