smart rock

a made-up categorization, term and catchword for multiple rock genres like psychedelic rock, experimental rock, prog rock, post-rock, space rock, art rock etc. (the same applies to metal genres) that tend to be more complex and diverse both lyrically, musically and technically than most genres of mainstream music, the lyrics tend to be more sophisticated and than your average pop song and common themes include:

philosophy, social criticism, psychology, politics, spirituality, poetry.

Although it is not uncommon for songs of these genres to be instrumental, as they are letting the music itself tell the story rather than vocals.

the music itself is more complex technically and longer and tends to focus more on the ambience (timbre) and technicality of the piece, rather than instrumentation and melody, although some genres are also known for being melodically and/or harmonically complex. Since this music is not intended to be mainstream, most of its listeners are a niche audience. So although "smart rock" is very good, not many people know it since it's usually anti-mainstream, but nonetheless it's still good music.

Although there are differences between those genres, the one similarity is that they all lean on experimentation and inventiveness.

Bands that could potentially fall into this categorization are bands like:
Tool, pink floyd, the doors, king crimson, porcupine tree, rush, radiohead, etc.

Dude 1: What music do you listen to?
Dude 2: Rock
Dude 1: Oh, you listen to AC/DC, Guns n'Roses, right? Maybe some Nirvana? Those are great bands man!
Dude 2: Nah, i'm more into psych rock, prog rock, you know all of those genres.
Dude 1: Oh, so you're into smart rock.
Dude 2: Yeah, man! (puts on headphones and listens to 35 minute prog rock track with 67 solos in one minute, talking about dragons and fantasy)