It means a cute nickname for the most amazing person you love.
You're my snoogali boo boo
When a friend of yours has recently started dating another, and is suddenly unable to attend and social gatherings because he is with said boo.
"What happened to Jim?" "He got a case of the Boo Flu, we won't hear from him until he is single again"
When you and your significant other are sharing a cigarette but they keep forgetting to pass it back to you for your turn.
Pass that cigarette back (man/woman), quit being a boo-gart.
When your girlfriend bursts into tears over the accommodations you've selected for your romantic getaway, you've booked a boo hoo hotel.
"CeCe saw the stains on the carpet and sheets and felt herself tear up. We both understood without a word. I'd picked a boo hoo hotel again, and no one was ever going to get lucky in that dump."
Hurting oneself physically or mentally out of your own confusion.
Mark: Hi boss remember that guy who ordered an open holster for his knife? He did forbidden boo boo to himself and He is suing us for cutting himself while using it in front carry...
Boss: ...