No, it isn't.
Synonym: Let down, Sad Antonym: Excited, Happy
A synonym of "dismayed" is bewildered. An antonym for "dismayed" is encouraged. Please see the related link below.
The antonym for "dismayed" is "reassured" or "comforted." While "dismayed" conveys feelings of shock, disappointment, or concern, its antonyms reflect a sense of calm, confidence, or relief. Other possible antonyms include "encouraged" or "elated," depending on the context.
Downcast and dismayed, Danny felt quite dejected when dumped by his girlfriend.
YES. Their reaction dismayed him. It can also be an adjective: He was dismayed at the change in his old friend.
He was dismayed at the thought of not seeing them again.
was dismayed to find that his partners political credit not good
A few synonyms would be: Abash, discouraged, disheartened, perplexed, put off, and many others. I would suggest Thesaurus.com to find good synonyms. It is an excellent source. Some antonyms would be encourage, or assure.
Gladdened.
pleasant surprise
They were not, however, dismayed by the news. The above sentence required two commas.
Some words that rhyme with dismayed are disobeyed, blade, and grenade.