The act of uncontrollably laughing, or having a giggle fit, at something that could actually be funny, or possibly not. A haver of a sillygasm will convulse while laughing, grab on to things tightly, and can not be easily stopped, as if they were having an orgasmic experience.
Guy: The joke wasn't that funny, but she just started having a sillygasm, I think she was drunk...
an amusing acronym disguised as a silly word. Dilligas stands for "do I look like I give a shit?" You can say it to your parents, your kid sister, your maiden aunt, really anyone who is annoying you, but whom you do not want to anger.
eddie: So anyway, as I was saying, to make a long story short, in other words, as God as my witness, between you, me, and the fencepost..................
freddie: hey man, dilligas?
eddie: what's that supposed to mean?
freddie: do i look like I give a shit?
eddie walks away angrily, muttering to himself.
freddie smiles, thanking his good fortune at discovering UD.