According to PrepEng, to "yeet" something is to throw it at high velocity, as well an exclamation used by the thrower while they're doing so. However, they also say that the word can be used as an exclamation of excitement or victory, giving the example of saying "yeet" after passing a test. Per The Sydney Morning Herald, it can work as an "excited 'yes'" and is "like 'yaaas' but for younger people" while it also "normally accentuates a poor decision or dumb idea". 

Confused? Dictionary.com describes it as "an exclamation of excitement, approval, surprise, or all-around energy, often as issued when doing a dance move or throwing something," so it looks as if it has a number of different meanings. They also mention, however, that we can say "ya yeet" instead, so that's another option. The word itself might be older than you think, too. It dates back to a Vine video from 2014, and since then the word has evolved over time (via Bustle). So, why not yeet yourself over to TikTok and see the word being used some more?