This is the 6127th most frequent Russian word.
страшной
"Страшной" means "terrifying" or "scary" in English.
In this sentence, 'страшной' is used as an adjective to describe 'ночью' (night), emphasizing a sense of fear or unease experienced during that time.
Это было страшной ночью.
It happened on a scary night.
Here, 'страшной' is used idiomatically to mean 'ugly', showing the word can have different meanings depending on the context.
Она всегда считала себя страшной.
She always thought of herself as ugly.
'страшной' in this case modifies 'фильм' (movie) to describe its horror genre or frightening content.