Here's what rhymes with astonishment.

Consider these alternatives

dismay / may disbelief / believe exasperation / operation consternation / information bafflement / agreement indignation / information delight / right elation / relation displeasure / never sorrow / tomorrow admiration / operation trepidation / education disdain / main irritation / operation disappointment / appointment regret / yet frustration / operation derision / given impatience / relations distaste / based skepticism / given jubilation / education bemused / used