Definition 1:
A long expression used in reaction when something unbelievably crazy has just occurred / been witnessed / someone has found out about.
Definition 2:
Can also be used to describe the actions of an individual or group, who has just completed something of remarkable skill or achievement, and are worthy of comparison to Batmans skills.
Derived from the Robin ‘The Boy Wonders’ TV show catchphrase;
“Holy (insert object / person / event here) Batman!!”
Example 1:
Greg: “I just saw two trains crash together, and everybody onboard walked off alive!”
The more polite, reference using version of "Holy Shit." Rather than Holy Shit, it uses Holy Shitakii Batman, Shitakii an asian mushroom, Batman, a widely-popular DC Comics character.
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.