Riffraff would be better if you said that as ''bullshit'' or ''trash'', and punk is usually said to people and it means asshole or fool, is commonly used to flame on somebody

Hahaha you have a very interesting question. Well first riffraff and punk are not the same. Riffraff bascially means nonsense. Example: Your kids are playing around and are being rowdy and noisy and you can say "What's all that riffraff about!?" Riffraff is not a term used today. It's very old slang. Well at least for Americans. Punk is a little harder to define and it actually has multiple definitions. 1. A punk can be a person who associates himself with punk rock music. Typically stereotyped as a bad, rude, and against society and/or government type of person 2. Calling someone a punk can also be an insult, however not a very strong insult and infact it's used a lot as a playful term between friends. Example: Your friend cuts in front of you in line you can say "You're a punk!". 3. It's also used as a synonym as a "whimp". If you're challenging someone to a fight and they don't want to you can call them a punk or say they're punking out (backing down). Hope this helps

I would almost never use it, except as a joke. It can refer to trash, something that you don't need. However, it can refer to two or more people who are unimportant and of low social standing. It is an insult when applied to people. You might hear it from other people. "I thought you said important people were going to be at this meeting, but all I see here is riffraff" "I usually don't associate with them on a social basis. Let's face it - they're basically just riffraff."