2: To bring about or compel by authority or force; 'The moderator invoked a rule causing the debate to be ended.'
6: An acronym for light amplification by stimulated emission of radiation.
8: Unique or specific to a person or thing or category.
10: A deciduous tree of the genus Quercus; has acorns and lobed leaves.
11: Female pronoun; a female, or something regarded as female, e.g. a ship.
13: Converts electrical signals into sounds loud enough to be heard at a distance.
19: The room where you sleep.
21: The plural form of 'duck.'
25: A United States unit of weight equivalent to 2000 pounds.
27: Gymnast's perfect score