Unimpressed means not amazed in the slightest by what you have just seen. The raised eyebrow, the flat right, then.
You are unimpressed by something, or unimpressed with somebody. British English leans on it as understatement: saying the manager was unimpressed usually means the manager was furious. It is a step beyond neutral — an unimpressed audience has judged the performance and found it thin. Much of the time the word describes a face rather than an opinion, which is why it so often follows looked or seemed.
1adjectiveunimpressedNot admiring or excited by something.
“The judges seemed unimpressed by his excuse.”
synonyms: unmoved
From un- + impressed.
Etymology from Wiktionary, CC BY-SA