Game on
When someone says 'Game on!', it means that they are accepting a challenge or ready to get something done.
Game plan
A game plan is a strategy.
Garbage fee
A garbage fee is a charge that has no value and doesn't provide any real service.
Garbage in, garbage out
If a computer system or database is built badly, then the results will be bad.
Gardening leave
(UK) If someone is paid for a period when they are not working, either after they have given in their notice or when they are being investigated, they are on gardening leave.
Gather pace
If events gather pace, they move faster.
Gather steam
If something gathers speed, it moves or progresses at an increasing speed.
Get a handle on
When you get a handle on something, you come to understand it.
Get a sheep skin
Getting a sheepskin (or your sheepskin) means getting a degree or diploma. (Sheepskin refers to the parchment that a degree is printed on- parchment comes from sheepskin.)
Get along famously
If people get along famously, they have an exceedingly good relationship.
Get away scot-free
If someone gets away scot-free, they are not punished when they have done something wrong. ('Get off scot-free' is an alternative.)
Get away with murder
If you get away with murder, you do something bad and don't get caught or punished.('Get away with blue murder' is also used.)
Get back on the horse that bucked you
When you start drinking again after being hungover from drinking the previous night.
Get in on the act
If people want to get in on the act, they want to participate in something that is currently profitable or popular.
Get in on the ground floor
If you get in on the ground floor, you enter a project or venture at the start before people know how successful it might be.
Get it in the neck
(UK) If you get it in the neck, you are punished or criticised for something.
Get it off your chest
If you get something off your chest, you confess to something that has been troubling you.
Get my drift
If you get someone's drift, you understand what they are trying to say. ('Catch their drift' is an alternative form.)
Get off the ground
If a project or plan gets off the ground, it starts to be put into operation.
Get on like a house on fire
If people get on like a house on fire, they have a very close and good relationship.