Like much plumbing

• Kind of baseball
• Like winter soccer, most likely
• Enclosed, as a pool
• Type of baseball
• ___ plumbing
• Like Astrodome events
• Sheltered from the elements
• Not for the outside

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
1711, from within door (opposed to outdoor ); the form indoors is first attested 1799 in George Washington's writings.

Wikipedia Word definitions in Wikipedia