1
general::
1. Complete the top portion of a building, as in They were scheduled to top out the dome next week. This idiom was first recorded in 1834. 2. Fill up a ship or complete its cargo, as in The ship was topped out with scrap iron. This idiom was first recorded in 1940. 3. Cease rising, as in Interest rates topped out at 10 percent. [Second half of 1900s] 4. Retire just as one becomes very successful, as in He decided that at sixty it was time to top out. [Colloquial; second half of 1900s]
American Heritage Idioms