Green’s Dictionary of Slang

1. abreast of the times, fashionable.

2000

G.V. Higgins At End of Day (2001) 79: Bob’s a really plugged-in guy — nothin’ major happens ’thout him knowin’ at least one guy that’s involved in it.

2. involved, connected; instinctively understanding.

1966		H.S. Thompson Hell’s Angels (1967) 159: Putting the word with a handful of bartenders, waitresses and plugged-in chicks who are known contacts.
1983		(con. 1970) S. Wright Meditations in Green (1985) 95: Seated in his chair Holly was plugged in, he experienced radiance.
1989		C. Hiaasen Skin Tight 100: I’ve still got a few friends in town . . . I’m still plugged in.
2008		‘Grandmaster Flash’ Adventures 80: We were in the groove. And I was plugged in. I had a natural sense of where the two records were spinning. [...] Felt like I was plugged into my own system, electricity running through my veins.
2012		M.F. Armstrong They Wished They Were Honest 59: Our new informant presented himself as being well plugged in to the gypsy hierarchy.
2020		Woods & Soderburg I Got a Monster 105: Rayam wasn’t plugged in like Gondo, though.