Meaning:

“老头” means “old men,” and “乐” means “joy.” Roughly translated as “old men’s joyride,” this term cannot be taken literally, since it refers to a type of low-speed four-wheeled electric vehicle often driven by seniors or the physically challenged in small cities in China. With an appearance not too different from the Mercedes Smart at first look, this type of vehicle is very cheap. An American vlogger specialized in rating vehicles named Jason Torchinsky posted several videos about the product, making it known outside China.

Example:

A: 你爸退休了吧？

Nǐ bà tuìxiū le ba？

Your old man has retired, right?

B: 退休好几年了。他现在每天开着老头乐去公园钓鱼。

Tuìxiū hǎojǐnián le。Tā xiànzài měitiān kāizhe lǎotóulè qù gōngyuán diàoyú。

He retired several years ago. Now he drives his low-speed electric car to the park, where he fishes every day.