Crowd means a large number of persons gathered together, however I've found some examples in which this expression is used "a large group of crowd".
In the future, these flying drones may be seen inspecting pipes or flying over a large group of crowds, streaming images. A Dragonfly Robot Taking Off
and
It's very rare to see large group of crowds congregating in one place in Seattle, the Folklife Festival is one exception.
It seems such usages are redundant, such as "large group of groups". My question: is this grammatically correct to use such expression?
Best Answer
Following the link and looking at the text preceding the first sentence, it soon becomes clear that the article was written by a non-native speaker of English. I would say that it's an error and perhaps reflects some idiom in the writer's own language.
I couldn't access the original text for the second quote for some reason. I would say that it may be a mistake but there is a possibility that it is intentional.
For example, at the Folklife Festival it is possible that each different attraction brings a crowd that is separated from other crowds. In that case the phrase would be acceptable but unusual.
Edit - I see that Dan Bron has given the same explanation as me with respect to the second point.