Green’s Dictionary of Slang

spout n.1

[spout v.1 ]

1. a religious or political orator.

[UK]Middleton Widdow of Watling-streete I iv: nich.: Our parson rails against players mightily, I can tell you, because they brought him drunk upo’th’ stage once. [...] corp.: I cannot blame him then, poor church spout.
[UK] ‘’Arry on the Elections’ in Punch 12 Dec. 277/2: I pelted the Radical posters, I guyed all the Radical spouts.

2. speechifying, haranguing.

[UK] ‘’Arry at the Play’ in Punch 2 Nov. in P. Marks (2006) 40: What I ’old is plays should be plays, and not hist’ry, or preachin’, or spout.

3. a large and ever-open mouth.

[UK]J. Ware Passing Eng. of the Victorian Era.