簡単めの語
▪decline formal to politely refuse to accept an offer or invitation, or refuse to do something :
▪ She has declined all offers of help.
▪ A palace spokesman declined to comment on the rumours. (Longman)
decline [dikláin] (4) 「申し出や招待を受けることを丁寧に断る、何かする事を断る」
▪deny to refuse to allow someone to do something or enter somewhere :
▪ They were denied permission to publish the book.
▪ He was denied access to the US. (Longman)
deny [dinái] (2) 「誰かが何かをしたりどこかに入ったりするのを許さない」
▪refuse to say firmly that you will not do something that someone has asked you to do :
▪ I asked the bank for a loan, but they refused.
▪ When they refused to leave, we had to call the police. (Longman)
refuse [v: rifjúːz, n: réfjuːs] (3) 「誰かにするように頼まれたことをしないことを強く言う」
▪reject to refuse to accept an idea, offer, suggestion, or plan :
▪ They rejected the idea because it would cost too much money.
▪ The Senate rejected a proposal to limit the program to two years. (Longman)
reject [v: ridʒékt, n: rídʒekt] (3) 「考え、申し出、提案、計画などを受け入れることを断る」
難しめの語
rebuff [ribʌ́f] (11) n はねつけ、vt (申し出など)をはねつける
Rebuff pertains to blunt or disdainful rejection: "He had ... gone too far in his advances, and had been rebuffed" (Robert Louis Stevenson). (American Heritage)
「ぶっきらぼうだったり尊大だったりする拒否」
repudiate [ripjúːdièit] (12) vt formal １．(申出など)を拒否する、(支払いなど)を拒む、２．公式に否定する、３．《古》縁を切る
repudiate implies a casting off or disowning as untrue, unauthorized, or unworthy of acceptance. <·teenagers who repudiate the values of their parents> (Merriam-Webster)
「関係を絶ったり、真実でない・公認されていない・受け入れる価値がない等として正当性を否定することを示唆」
spurn [spə́ːrn] (11) vt literary (申し出など)をはねつける
spurn stresses contempt or disdain in rejection or repudiation. <·spurned his overtures of friendship> (Merriam-Webster)
「拒絶や拒否の中の軽蔑や高慢を強調」
veto [víːtou] (10) vt １．(法律など)に拒否権を発動する、２．(提案など)を断る、nUC １．拒否権、２．拒否
▪veto to officially refuse to allow a law or plan, or to refuse to accept someone's suggestion :
▪ Congress vetoed the bill.
▪ The suggestion was quickly vetoed by the other members of the team. (Longman)
「法律や計画を認めることを公式に拒否する、人の提案を受けるのを断る」
参照 (類義語比較)
American Heritage refuse
https://www.thefreedictionary.com/refuse
Longman refuse
http://1.vndic.net/index.php?word=refuse&dict=longman_en
Merriam-Webster decline
https://www.merriam-webster.com/dictionary/decline
Random House refuse
http://www.dictionary.com/browse/refuse