This is the 1465th most frequent German word.
rainer
"Rainer" is a German male given name, equivalent to "Rayner" or "Ragnar" in English.
In this sentence, "Rainer" is used as a proper noun, which is a common German male first name.
Rainer ist ein sehr talentierter Musiker.
Rainer is a very talented musician.
Here, "rainer" serves as the comparative form of the adjective "rainy" in German, which is established as 'regnerischer' in standard German.
Bei strömendem Regen dachte ich nur: 'Es könnte gar nicht rainer sein.'
In pouring rain, I only thought: 'It couldn't be rainier.'
In this instance, "Der Rainer" includes a definite article, indicating familiarity and casual reference to a person named Rainer.