N-PLURAL represents plural noun according to the explanation in the Collins COBUILD dictionary. Can I interpret it as a noun that is countable but unable to be used in singular form and only able to be used in plural form?
1This could easily have been added to the first question. Also, I don't think a clear, correct, definitive answer has been given to the first one yet.– Alan CarmackAug 9, 2016 at 13:15
Dictionaries should usually include a usage guide that explains what things like N-PLURAL mean, but yes, your guess is basically correct. Trousers is one of the nouns in English that can really only be used in a plural form:
He wore trousers
He wore a trouser
There are a few words like this: trousers, pants, scissors, clothes, glasses (but only when it means "reading glasses" - drinking glasses can be singular). These words are technically called plurale tantum.
There are many usages of a scissor as a noun. Check out Google books for 21st century uses only. It's also used earlier (20th century, etc). Aug 9, 2016 at 13:19
OK, scissors isn't always plural...just the vast majority of the time, including historically. For the learner of English, I would say that a pretty good first approximation is that scissors is always plural.– stangdonAug 9, 2016 at 14:35