How do I list occupation if I'm retired but do occasional Speech Language Pathology jobs?

The IRS only uses "occupation" for statistical purposes----whatever you enter for occupation has no effect on your tax due or refund.   If you want to call yourself a "retired speech pathologist" you could.

For the occupation question, you can enter retired, language pathologist, or anything you want, really - it does not affect anything on your tax return.

If you have self-employment income and expenses to enter, you can do that by preparing a Schedule C.    How do I start a Schedule C?