This is the 14019th most frequent German word.
geheimes
"Geheimes" means "secret" in English.
Here, 'geheimes' is used as an attributive adjective ('geheime') to describe the noun 'Treffen', indicating that the meeting is secret or confidential.
Das geheime Treffen fand gestern statt.
The secret meeting took place yesterday.
In this sentence, 'geheimes' is again an attributive adjective ('geheimes') modifying the noun 'Versteck' to imply that the hiding place is secret.
Er hat ein geheimes Versteck in der Nähe.
He has a secret hiding place nearby.
Here, 'geheimes' is used as an attributive adjective ('geheimes') for the noun 'Projekt', signifying confidentiality pertaining to the project.