The standard definition of a dungeon crawl is:
"A dungeon crawl is a type of scenario in fantasy role-playing games in which heroes navigate a labyrinthine environment (a "dungeon"), battling various monsters, and looting any treasure they may find."
For me it involves any game in which you have to go through one or many dungeons because that's where *most* of the action happens.
The rest is flexible. It can have more or less roleplaying, more or less mechanics. You're in a dungeon, you loot shit, you beat strong enemies and you clear it. That's it.
Though the genre is broad the feeling of it is very specific: I'm in a dungeon, I have been here since fucking forever and I don't know if I'm going to survive this because it's boiling with enemies, puzzles, traps and possibly bosses too, but also wondrous treasures. When you see the exit or save room in a dungeon crawling game you feel relieved and good because you made it so far in once piece. The problem is that following that definition shit like Symphony of the Night or even Vampire the Masquerade: Redemption. might be considered dungeon crawlers or with dungeon crawling elements. ARPGS, Rogue-likes… you name it, but these don't exclude the tag dungeon-crawler.