Gloss vs dictionary extensions

	Gloss	Dictionary extensions
Tells you what the word means in this sentence	Yes — the meanings are ranked by the sentence	No — every meaning, in dictionary order
Shows the meaning you want first	Right about three times in four	You scroll
Shows an example of the word in use	Yes, from the dictionary's own examples	Sometimes
Synonyms and opposites	Yes	Sometimes
Works offline	Yes — the dictionary is inside	Usually yes
A reading mode that underlines the words you do not know	Yes	No

Pick a dictionary extension if

you want a quick lookup of a word you half know, and you are happy to skim the meanings. They are good at that, and several of them are excellent.

Pick Gloss if

you are reading something dense — a newspaper, a paper, a book — and the words you do not know are the ones whose meaning depends on the sentence. That is the case a dictionary popup cannot help with, because it cannot see the sentence.

Try it here — the demo is the real engine, and the word sanguine appears twice with two different meanings.