Can be used as an adjective, or an exclamation. Essentially, it's a basic ass white girl way of saying "yea" or "yes." As an adjective, it describes anything trendy, basic, unnecessary and overdone, especially if it's something you'd see a 14-year-old basic white girl post it on Instagram. Selfies that are overly posed and have a shitload of filters on them, long, trendy ombre hair, "wish I had a relationship like this" posts on Instagram, and generally, anything like that could be described as "yeaum."
Typhani, is that a new Michael Kors bag?
"Yeaum."
That girl is so fucking basic. Her whole aesthetic seems ripped from some Tumblr page. Seriously, is there any originality? She's just so...."yeaum."