faldstool

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A folding chair or stool, especially one used by a bishop when not occupying the throne or when presiding away from the cathedral.
• noun A desk at which the litany is recited.
• noun A small desk at which worshipers kneel to pray, especially one at which the British sovereign kneels at the time of coronation.

from The Century Dictionary.

• noun Formerly, a folding chair similar to a camp-stool, especially one used as a seat of honor and an ensign of authority, probably having this character from the ease with which such a seat could be carried with an army on the march, and could be set up when required.
• noun Hence A seat having the form of the above, but not capable of being folded.
• noun A folding stool, provided with a cushion, on which worshipers kneel during certain acts of devotion; especially, such a stool placed at the south side of the altar, at which the kings or queens of England kneel at their coronation.
• noun A movable folding seat in a church or cathedral, used by a bishop or other prelate when officiating in his own church away from the throne, or in a church not under his jurisdiction.
• noun A small desk in cathedrals, churches, etc., at which the litany is enjoined to be sung or said.

from the GNU version of the Collaborative International Dictionary of English.

• noun A folding stool, or portable seat, made to fold up in the manner of a camo stool. It was formerly placed in the choir for a bishop, when he offciated in any but his own cathedral church.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A portable, folding chair used by a bishop when away from his throne
• noun Any similar stool used in a divine service (such as a British coronation)