adult

To express this sign you can use a version of the sign "grow up." What you do is you move the sign very quickly to the last part of the sign. And then you hold it for a very small amount of time longer than you do the sign "grow-up."
RAISED/GROW-up/ADULT:

Here is another variation of ADULT.
You can use one of the versions for the sign for "tall." Hold a bent hand by your forehead and then move it up and out a bit.

Here is another version of adult.
Some people say this is "signed English" but I notice that many d/Deaf people use it.

ADULT:

Note: If you replace the "A" with a "T" it means "teenager."
Some people feel that you should sign teenager by signing "young."