When a person is completely and utterly socially awkward. For example, they seem to say nothing when something should be said and as a result can come off creepy. Or, they say the completely wrong thing. This person will often act like they absolutely hate what they are doing and cannot wait until it's over.
For example, if a rookie messes up on something they've never done before and the response by one to act a sherm
is "that was terrible."
Guy 1: ...(stares)
Guy2: don't act a sherm
, bro. Say something.
Can also be used: actin a sherm.
John: did you see that new IT guy?
Gregg: yea. He was all actin a sherm