Informal:
* Old: This is the most straightforward slang term, often used playfully or sarcastically.
* Ancient: This implies a very old age, often used humorously.
* Geezer: A more informal and slightly derogatory term for an older man.
* Granny: A playful or affectionate term for an older woman.
* Senior: This is a more polite and respectful term for someone who is older.
More informal and sometimes derogatory:
* Old geezer: This is a more informal version of "geezer."
* Has-been: This implies that someone is past their prime.
* Fossil: This is a very derogatory term for someone who is old and out of touch.
Other options:
* Vintage: This implies that something is old but still valuable.
* Classic: This is used for things or people who are old but still admired.
The best word to use depends on the specific situation and your relationship with the person you're talking about.