This is the 10868th most frequent Russian word.
вымершего
"Extinct."
The word 'вымершего' is used as an adjective in the genitive case describing the 'species' belonging to an extinct category.
Мы посетили музей, где была реконструкция вымершего вида динозавра.
We visited the museum where there was a reconstruction of an extinct dinosaur species.
Here, 'вымершего' is an adjective in the genitive case modifying 'tribe', indicating that it has ceased to exist.
Это книга о жизни вымершего в прошлом веке племени.
This is a book about the life of a tribe that became extinct in the last century.
In this context, 'вымершего' is used as an adjective in the genitive case referring to 'animal', signifying its extinct status.