This is the 17279th most frequent Russian word.
суше
The Russian word "суше" refers to "land" or "dry land" as opposed to water.
The word 'суше' here comes from the noun 'суша' (dry land) and is used as a comparative form to indicate 'on land'.
На суше легче дышать, чем в воде.
It is easier to breathe on land than in water.
In this sentence, 'суше' functions as the comparative form of the adjective 'сухой' (dry), meaning 'drier'.
Суше стало после того, как дождь прекратился.
It became drier after the rain stopped.
Here, 'суше' is part of the expression 'на суше,' referring to 'on land' (the dry part of the earth's surface).