Similar word to yawner:

accustomed, apathetic, blah, boring, dead, depressed, draggy, even, falling off, flat, inactive, inert, languid, lifeless, listless, monotonous, placid, quiet, regular, routine, sitting tight, slack, slothful, slow, sluggish, stagnant, still, stolid, tight, torpid, unexciting, unresponsive, usual, without incident, yawn