From Wordsmith's list:
Calcar
Calīcar
n. 1. (Glass manuf.) A kind of oven, or reverberatory furnace, used for the calcination of sand and potash, and converting them into frit.
1. (Bot.) A hollow tube or spur at the base of a petal or corolla.
2. (Zoöl.) A slender bony process from the ankle joint of bats, which helps to support the posterior part of the web, in flight.
3. (Anat.) A spur, or spurlike prominence.