To grip something is to hold and control it. This word can be used as a verb or as a noun, but it’s usually in the form of a noun:
Let me a get a grip on this couch before we move it.
Do you have a good grip on that?
Check your grip.
Don’t lose your grip!
Tom lost his grip on the box and dropped it.
The police officers gripped the man by both arms as he was lead away from the courtroom.
If you don’t grip your phone tightly enough, you might drop it. (grip = hold. The word "hold" is probably better.)
It’s important to have a strong grip on a football before throwing it.
Vince has a strong grip. I could feel it when I shook his hand. (This is the kind of thing that a man might say after shaking another man’s hand. Some men squeeze hard when shaking hands. It’s rarely said of a woman because women don’t squeeze hard when they shake hands with another person.)
Grip the football tightly before you throw it.
The word "grip" is commonly found in spoken English when talking about a person’s control over something (tangible or intangible):
You’ve got to get a grip. (get a grip = stop acting foolishly or try to control yourself)
You’ve got to get a grip on yourself.
Donald doesn’t have a firm grip on reality. (a firm grip = understanding)
It’s time to come to grips with what’s happening. (come to grips = be realistic)
The leader of the country lost his grip on power and was ousted from his position. (lose one’s grip = lost control)
This word is also used to refer to that part of a bicycle or a motorcycle where your hands go to steer the vehicle:
The grips on my bike are made of some kind of rubber.