How to sign "forget" and phrases in American Sign Language (ASL)?
Definition: Fail to remember or recall; not remember.
Pronunciation/articulation: Dominant horizontal "B-thumb -> 15" handshape, palm in, slides across the forehead rightward.
Meaning: slips one's mind.
Related signs: slip mind, blank out.
Opposite: REMEMBER.
forget it:
Meaning: An injunction to put something out of one's hopes, concern, etc, esp because it is impossible.
Variation: Oh, it was nothing important -- forget it."
Also sign synonyms found in NEVER-MIND.
First 100 words.
As you feel more comfortable with the first few hundreds of ASL signs, progress further with your vocabulary and learn signing more.