When someone is unable to process things, resulting in an absolute confusion and inability to speak normally. Normally used as internet slang, in moments such as public voice chats or texting chatrooms.
"did you hear about theo yesterday"
"yeah i heard he had a total miso moment"
An admission of jealousy. "I'm so jealous". An adaptation of the phrase "miso horny", which is a mutation of the phrase "me so horny", which is a poorly translated version of the phrase "I'm so horny". But with jealousy instead of horn.
Miso jelly could also conceivably be a type of food, which facilitates humourous use of the phrase as a pun.
"OMG you got the latest iButtPlug, MISO JELLY"
"What's the matter baby? Can't finish your supersized bowl of miso jelly?"