Simple:
* The boxer landed a powerful punch with his forearm.
* She braced herself against the wall, using her forearms for support.
* The doctor checked the patient's forearm for a pulse.
More complex:
* He flexed his forearm muscles, demonstrating his strength.
* The artist carefully traced the outline of the flower with the tip of her forearm.
* Her forearm was adorned with a intricate tattoo, a testament to her personality.
* The weightlifter's forearms bulged with each rep, showcasing years of dedication.
Figurative:
* The politician's speech was a forearm to his opponents. (Meaning it was a strong attack)
* The lawyer argued his case with the forearm of a seasoned professional. (Meaning he was very skilled and persuasive)
Remember, the context of the sentence will determine the best way to use the word "forearm."