noun
having a romantic interest; having a chance; having a pulse
Colloquial expression used mainly in romantic contexts to mean someone shows signs of interest, or more broadly for any favorable prospect. The literal 'having a pulse' sense is rare in modern usage.
Antonyms: 脈なし
彼女、脈ありだと思う？
Do you think she's interested?
面接の手応えは悪くなかった。脈ありかも。
The interview went well. I might have a chance.