The Collaborative International Dictionary of English v.0.48:
Prosiness \Pros"i*ness\, n. The quality or state of being prosy; tediousness; tiresomeness. [1913 Webster]WordNet (r) 3.0 (2006):
prosiness n 1: commonplaceness as a consequence of being humdrum and not exciting [syn: prosiness, prosaicness]