g#: Galaxy # (an Infinity that reaches the #th galaxy, as can be seen under Statistics tab)
Big Crunch/Crunch/Infinity (verb): The act of clicking the Big Crunch button, resetting all lower soft resets to gain Infinity Points
pre-Infinity (noun): The part of the game before you've clicked Big Crunch once
Infinity # (noun): The part of the game after you've clicked Big Crunch # times. Infinity 0 is the same thing as pre-Infinity
Infinitied Stat: As seen on Statistics. At first this is how many times you've Infinitied, but some upgrades and achievements increase this number even further. Some upgrades use this to boost production. Sometimes shortened to "Infinitied".
OoM: Order(s) of Magnitude. One order of magnitude = 10x the previous amount. Used to refer to progression (e.g. I've gained another OoM of Infinity Points)