Is "subcopy" a word?

A copywriter just sent me over a copy deck that had the word subcopy to describe the text immediately after the page title. Up until now I had been referring to it as a description.

Example:

TITLE

Going to the park.

SUBCOPY

I can still remember the days of my youth when a trip to the park was ...

BODY

...

Is subcopy a word and does anyone have a better alternative?

I worked in the Tokyo office of a New York-based ad agency over 30 years, both on the creative and account-service sides. Actually, I wrote copy for many ads. We used to call the title of ad copy and the following summation of copy text “Catch phrase (copy) / Sub-catch,” “Headline / Sub-head,” "Title / Sub-title," or “Caption” and “Lead copy” at that time.

I don’t think I ever heard of “Sub copy” when I was on the front lines of the ad business. But I don’t know the recent jargon of copy writing, as I left the business long ago.