Meaning:

“精神”when used as an adjective means “energetic” and “looking neat,” and “小伙” refers to “young men.” Originally used to describe an energetic and cute young guy, especially in northern China dialects, the term is now used by netizens to refer to the kind of young guys who dress themselves in the corny style often seen in mafia members and rappers, wearing items such as tight pants, T-shirts with big logos and bright-colored moccasins. They also wear conspicuous tattoos and brag a lot, trying to create the impression that they are street-smart.

Example:

A: 你弟弟找到工作了吗？

Nǐ dìdi zhǎo dào gōngzuò le ma?

Has your younger brother found a job?

B: 还没。他最近天天和一群精神小伙混在一起，常常不回家。

Hái méi。Tā zuìjìn tiāntiān hé yīqún jīngshén xiǎohuǒ hùn zài yīqǐ, chángcháng bù huíjiā。

Not yet. He’s hanging out with a bunch of punks lately and seldom comes home.