Mawkish means excessively sentimental or so sappy it's sickening. Which is how you'd describe two lovebirds gushing over each other or your grandma’s cooing, cheek pinches, and sloppy-lipstick kisses.
The adjective mawkish came into vogue in the 1600s. Oddly enough, it's rooted in the Middle English word maggot and originally meant “sickly or nauseated.” But mawkish eventually evolved to mean something so overly sentimental it makes you sick. It's not a word you hear very often these days, but feel free to use it to describe really lame love poems and annoyingly mushy Valentine's Day cards.