IPA: /ˈɜːrk.sə.məs/
KK: /ˈɜrksəmnəs/
The quality or state of being annoying or bothersome.
The irksomeness of the constant noise made it hard to concentrate.
Irksomeness is formed from "irksome" (from Old English "earcian", meaning to be troublesome or annoying) and the suffix "-ness" (meaning the state or quality of). The word refers to the state of being annoying or troublesome.
Think of the word 'irksome' which means annoying, and remember that 'irksomeness' describes the quality of being annoying.