This is the 9737th most frequent Japanese word.
落選
"落選" means "failure to be elected" or "not being chosen."
In this sentence, '落選' refers to the act of losing in an election.
彼は次の市長選挙で落選しました。
He lost in the next mayoral election.
Here, '落選' describes the experience of election loss.
彼女が落選を経験した後、より良い政策を作るよう努力しました。
After experiencing defeat in the election, she worked hard to create better policies.
In this instance, '落選' is used as the noun meaning 'loss in election.'