sheeesh is a word used by today's youth and an expression for something that has happened. you take your two fingers and point them high up on your forearm to check if you still have a pulse. It can be compared like "omg", "wow", "crap", "damn". It can be expressed for positive things as well as negative things. Whoever thought of this must have been a very, very intelligent person….
Dan: Check out the hot pic Emily posted on Instagram today
Jim: Sheeesh, she's hot as hell
cassy: my mom found out today that my dad is having an affair with our pool boy.
Susan: Seeesh