Meaning:

“最” means “most,” “靓,” a word from Cantonese dialect, means “pretty,” “的” is a marker for an attributive (in this case “最靓”) and “仔” is the Cantonese for “boy.” Literally translated as “the best-looking boy,” this term is the title of a Chinese pop song and has been used by netizens jokingly to describe the most eye-catching person or thing in a certain situation.

Example:

A: 你去看车展了吗？

Nǐ qù kàn chēzhǎn le ma？

Did you go to the auto show?

B: 去了，蔚来新推出的一款车是全场最靓的仔。

Qù le，wèilái xīn tuīchū de yīkuǎnchē shì quánchǎng zuìliàng de zǎi。

Yes, I did. A new model electric vehicle from NIO was the most eye-catching car at the show.