A feminist notion that emotions are somehow hard work, and that they should be financially compensated for them. Men don't seem to have a problem being nice to people, and are rightfully perplexed when women use this term.
Given the amount of emotions a normal woman has every few minutes, about virtually everything, emotional labor seems to be an oxymoron.
"Omg, Brad's such a bad manager, he doesn't recognize all the emotional labor I put in, trying to be nice to customers all the time!"
Emotional labour was originally a word for people who have to put a lot of uncompensated emotional effort into their job. Recently, however, it's more along the lines of "idk, it kinda sucks when I have to listen to my boyfriend" or "now that I've made my statement, I don't want to defend myself or back it up because it's emotionally laborious"