Has multiple meanings. Mainly used as an adjective which meanings depend on the tone. In a disgusted tone peligroso describes something gross or not likeable. In a positive tone it can mean something that is very cool or Ludacris. You can also use it to mean dangerous which is its spanish translation.
"Hey Carmen your outfit is looking pretty peligroso!"
"Yo Coco that shit is peligroso!
"Ew! Bitch get that peligroso shit out of my house!"
"Suki your cookies are peligroso!"