Unappetizing describes food that LOOKS like it will not taste good. The judgment happens through your eyes, before your mouth gets involved — grey meat, a limp sandwich, a school lunch tray, a cold pizza that has gone hard. That is the heart of the word and where it differs from tastes bad or disgusting. Unappetizing is about the appearance killing your appetite. Food can be unappetizing and still be delicious — plenty of the best Taiwanese food looks alarming to a first-time visitor. Good writers use the word exactly for this gap. It also stretches beyond food. 'An unappetizing prospect' means a situation you do not want to face — a long meeting, a difficult conversation. Here it keeps the food flavour: the thing sits in front of you and you have no appetite for it. Both spellings exist: unappetizing is the American spelling and now common everywhere; unappetising with an s is British. Neither is wrong. It is a mild, polite word. If a guest says your dish looks unappetizing, they are being careful with you — the blunt words would be much worse.

看起來不好吃的、倒胃口的。台灣講「賣相不好」最貼切——重點在「看起來」，不一定真的難吃