unentdeckt
undiscovered
Not yet found, seen, or noticed.
Der Schatz soll seit Jahrhunderten unentdeckt in der Höhle liegen.
The treasure is said to have lain undiscovered in the cave for centuries.

undiscovered
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undiscovered
Not yet found, seen, or noticed.
Der Schatz soll seit Jahrhunderten unentdeckt in der Höhle liegen.
The treasure is said to have lain undiscovered in the cave for centuries.

The word is built simply: it consists of the negative prefix 'un-' and 'entdeckt' (discovered), the past participle of the verb 'entdecken' (to discover). So it literally means 'not discovered'.
Viele Tierarten in der Tiefsee sind noch völlig unentdeckt.
Many animal species in the deep sea are still completely undiscovered.
This adjective is very often used in the fixed combination with the verb 'bleiben' (to remain). The phrase 'unentdeckt bleiben' means that something or someone continues not to be found or noticed.
Der Dieb hoffte, unentdeckt zu bleiben.
The thief hoped to remain undiscovered.
You can tell from the noun whether an undiscovered talent or an undiscovered place is meant. If 'unentdeckt' (undiscovered) refers to a person or an ability ('Talent' — talent, 'Künstler' — artist), it is about unrecognized ability. If it refers to a place or object ('Schatz' — treasure, 'Insel' — island), it is about not having been found.
In ihm schlummert ein unentdecktes musikalisches Talent.
An undiscovered musical talent lies dormant in him.
unknown
'unbekannt' and 'unentdeckt' are close in meaning because in both cases someone or something has not yet entered other people's awareness. 'unbekannt' says generally that you do not know something, or that someone is not famous. 'unentdeckt' fits especially when something has not yet been found, seen, or noticed. With people, it can also refer to a talent that no one has encouraged yet. The words can be confused, but 'unentdeckt' sounds more strongly connected to searching, finding, or potential. 'unbekannt' is more general.

Im Wald blieb die alte Höhle jahrelang unentdeckt.
The old cave remained undiscovered in the forest for years.
Dieses kleine Dorf ist vielen Reisenden noch unbekannt.
This small village is still unknown to many travelers.