Adjective

(en adjective)

hideous or frightful

* Shakespeare

So bad a death argues a monstrous life.

enormously large

a monstrous height

a monstrous ox

freakish or grotesque

* John Locke

a monstrous birth

* Jeremy Taylor

He, therefore, that refuses to do good to them whom he is bound to love is unnatural and monstrous in his affections.

of, or relating to a mythical monster; full of monsters

* Milton

Where thou, perhaps, under the whelming tide / Visitest the bottom of the monstrous world.

(obsolete) marvellous; strange

Adjective

(en-adj)

Dreadful; causing alarm and fear.

Formidable, powerful.

* 1883: (Robert Louis Stevenson), (Treasure Island)

and there was even a party of the younger men who pretended to admire him, calling him a "true sea-dog," and "real old salt," and such-like names, and saying there was the sort of man that made England terrible at sea.

Intense; extreme in degree or extent.

* {{quote-book, year=1963, author=(Margery Allingham), title=(The China Governess)

, chapter=18 citation , passage=‘Then the father has a great fight with his terrible conscience,’ said Munday with granite seriousness. ‘Should he make a row with the police […]? Or should he say nothing about it and condone brutality for fear of appearing in the newspapers?}}

Unpleasant; disagreeable.

* , chapter=12

, title= The Mirror and the Lamp , passage=To Edward […] he was terrible , nerve-inflaming, poisonously asphyxiating. He sat rocking himself in the late Mr. Churchill's swing chair, smoking and twaddling.}}

Very bad; lousy.

* {{quote-news, year=2012, date=April 26, author=Tasha Robinson, work=The Onion AV Club

, title= Film: Reviews: The Pirates! Band Of Misfits , passage=The openly ridiculous plot has The Pirate Captain (Hugh Grant) scheming to win the Pirate Of The Year competition, even though he’s a terrible pirate, far outclassed by rivals voiced by Jeremy Piven and Salma Hayek.}}