Seems like it's a very ancient word. In Russian "cucumber" also pronounces as "agurets" ("огурец").
On an unrelated note, anguria means watermelon in Italian (in the South of Italy cocomero is more frequent).
Just to confirm: "αγγούρι" is pronounced /aŋ.gu.ɾi/, right? When reading the whole sentence, the audio seems to say it like that, but when I hover over the word in isolation, it just sounds like /a.gu.ɾi/.
Both pronunciations are used, but /aŋ.gu.ɾi/ is more common as Wiktionary denotes. Pronounciations depend on the speaker and the region where (s)he lives. Although /aŋ.gu.ɾi/ is more common, I personally pronounce it as /a.gu.ɾi/, because I live in the northern part of the country.
Α similar situation occurs with the word τομάτα (tomata). Many people (me included) pronounce this word as domata and spell it ντομάτα. For more information click here
Well - on the Wiktionary it says that "τομάτα" is an alternative form. Why isn't the more common form "ντομάτα" used? I'm also curious if there is an "official pronunciation" on TV and radio ...
You should avoid /a.gu.ɾi/. It's not grammatically correct. Language teachers stress it all the time: "Don't forget the N!!" :) I would add that it generally indicates low educational level and poor knowledge of the language.
Funny that "αγγούρι" looks and sounds somewhat like "αγόρι". Even the stress is at the similar place.
In a listening exercise, you should use the spelling corresponding to what the voice says, not a different spelling corresponding to a different pronunciation -- even if that might be what you yourself would say.
In the normal-speed audio I heard ντομάτα. When it was marked wrong I listened to the slowed version, which does indeed say τομάτα. I nearly submitted a report of wrong audio ...