Chuckle in my head. It's the latest and greatest replacement of LOL because that is way over-used and sometimes, you really shouldn't laugh out loud. Like, when you're at a funeral, and your sister (sitting right next to you) texts you to let you know that your grandmother's dress is tucked into the back of her underwear. The appropriate thing to do would be a private, internal chuckle.
Don't look know, but Nana's dress is stuck in her thong. CIMH!!