Mizuuki Tsujimura の 'Lonely Castle in the Mirror' を読んでいます。
'It's such a surprise,' Aki shot back. 'Whether I'm interested or not is beside the point. I'm just so astonished that you'd even think of bringing us presents, Masamune.
' 'You're so annoying. If you're going to diss them, then give them back. It took time to get all this stuff together, you know.'
"diss" は先日取り上げた "fess" と同様に、元になる "dis + xxx" 言葉の略語の様ですが、 "dis + xxx" は沢山あるので直ぐには検討がつきません。文脈から見当が付かないといけないのでしょうが、せっかちなので辞書を見ます。
・Collins Dictionary: If someone disses you, they criticize you unfairly or speak to you in a way that does not show respect.: [informal] He believes that his records speak for themselves and ignores those who diss him.
・Cambridge English Dictionary: to disrespect: Don't diss me, man!
・Merriam-Webster: to treat with disrespect or contempt: dissed her former co-star in the interview
・Vocabulary.com: treat, mention, or speak to rudely: “the student who had betrayed his classmate was dissed by everyone”
"disrespect" から来た略語でした。"diss someone" の場合上記の辞書の説明にある意味になるのですね。