na-adjective, noun
Describes a situation, period, or path that is full of hardships, obstacles, or difficulties. Often used in set phrases like 多難な時代 or 前途多難.
彼の人生は多難だった。
His life was full of troubles.
前途多難だが、あきらめない。
The road ahead is difficult, but I won't give up.
困難 is a more common and general word for 'difficulty' or 'hardship'. 多難 emphasizes that there are many difficulties or troubles, often implying a series of obstacles.
Compound of 多 (many) and 難 (difficulty, trouble). The meaning is transparent from its components.