What is Speaker?

Legal Definition
The presiding officer of the house of representatives of the United States is so called. The presiding officer of either branch of the state legislatures generally bears this name.
-- Bouviers Law Dictionary
Legal Definition
This is the official designation of the president or chairman of certain legislative bodies, particniarly of the house of representatives in the congress of the United States, of one or both branches of several of the state legislatures, and of the two houses of the British parliament The term "speaker," as used in reference to either of the houses of parliament, signifies the functionary acting as chairman. In the commons his duties are to put questions, to preserve order, and to sce that the privileges of the house are not infringed; and, in the event of the numbers being even on a division, he has the privilege of giving the casting votfe. The speaker of the lords is the lord chancellor or the lord keeper of the great seal of England, or, if he be absent, the lords may choose their own speaker. The duties of the speaker of the lords are principally confined to putting questions, and the lord chancellor has no more to do with preserving order than any other peer. Brown.
-- Black's Law Dictionary