"Spool" (spa-pool hybrid)

[James Callan]

My mother-in-law just moved to Arizona, and she's got a spool in her
backyard. As the name suggests, it's a combination between a spa and a
pool -- larger than a regular spa, shallower than a regular pool, with
water jets and a heating element.

Googling for combinations of "spool", "spa" and "pool" along with terms
such as "hybrid" or "combination" turns up thousands of mentions,
including:

http://www.tucson.com/story/homes/madden/THsp04/THsp04_whats_in.html

With today's smaller yards and hectic lifestyles, the spool is becoming
ever more popular. What's a spool? Essentially a small pool/fairly large
spa hybrid. Most are between 12 and 20 feet long and 8-12 feet wide. Many
have contoured benches, varied jet heights, and loungers built in.

http://www.slowfattriathlete.com/newport.htm

They have a house with more games and toys than you can count on your
fingers and toes, and a "spool" in the backyard, an imaginatively
sculpted spa-pool hybrid that feels like a luxury resort and is perfect
for soaking out any post-triathlon aches. And Indigo is more fun than a
crate full of sock monkeys.

Many of the sources are based in Arizona, but I've found mention of
spools in Texas and Florida.

This sense of "spool" is not in the OED online.

 -- James Callan