Dana Milbank writing in The Washington Post:

‘In conventional usage, sarcasm, from the Greek “sarkasmos,” or sneer, means to use irony in a cutting way — often enthusiastically stating the opposite of what one means. But like all pioneers in the field of comedy, Trump has shifted the boundaries so that “sarcastic” means, roughly, “a term applied retroactively to something I wish I hadn’t said.”
For example…’