The German adjective and adverb dicht sounds a lot like the English word "thick," and while there are cases where it can be translated as "thick," it's the exception rather than the rule. Let's take a look today at the different ways that dicht can be translated in formal and informal contexts.

Dicht is often translated into English as "dense" or "densely," or in the case of dichter, "denser":

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Er sollte dehnbar sein, und je dichter, desto besser.

It should be stretchy, and the denser, the better.

Caption 79, Coronavirus - Schutzmasken zum Selbermachen

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Die Kaimauer des Südhafens ist dicht mit Seescheiden besiedelt.

The quay wall of the south harbor is densely populated with sea squirts.

Caption 13, Abenteuer Nordsee - Unter Riesenhaien und Tintenfischen

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It's also common to see dicht translated as the adjective "close" or the adverb "closely":

Die kommen ganz dicht dran.

They come very close.

Sie beachtet die Leute überhaupt nicht, die Besucher.

She doesn't pay attention to the people, the visitors at all.

Caption 43, Für Tierfreunde - Geparden

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Darin warten etwa 3.600 kleine Zähne,

Inside await roughly 3600 little teeth

die in mehr als 300 dicht zusammenstehenden Reihen angeordnet sind.

that are arranged in more than 300 closely set rows.

Captions 66-67, Evolution - Meeresbewohner

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In slang usage, dicht machen can mean "to close": 

Komm, wir machen hier dicht.

Come on, let's close up here.

Caption 15, Die Pfefferkörner - Alles auf Anfang

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Frau Korff kann dicht machen, ich verliere meinen Job,

Ms. Korff will have to close the business, I'll lose my job,

Caption 2, Großstadtrevier - Von Monstern und Mördern

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A rather unexpected formal usage of dicht conveys that something is sealed, in the sense of "not leaking": 

Das Boot ist dicht.
The boat is sealed.

Das Fass hält nicht mehr dicht.
The barrel is no longer sealed.

Probably related to dicht halten as “to keep sealed,” dichthalten is a slang way of referring to keeping a secret, in a similar sense to "my lips are sealed":

Bitte halte dicht, psst...

Please keep it a secret, shhh...

Caption 7, JoNaLu - Wo ist Rosalie?

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When you rather rudely call somebody "thick" in English, you're saying that they are slightly crazy or stupid. But in German slang, you'd say nicht ganz dicht, the suggestion being that thoughts are "leaking" out of someone's head:

Johannes ist nicht ganz dicht.
Johannes is a crazy.

Last but not least, dicht may be formally translated in certain contexts as "thick": 

Das Wetter heute: Vormittags dichter Nebel, nachmittags sonnig.
Today's weather: morning thick fog, afternoon sunny.

Further Learning
Go to Yabla German and search for dicht to see the many different ways it is used in a variety of real-world contexts.