single-shot (firing one shot at a time); a single-shot gun
古い単発の猟銃は扱い方に注意が必要だ。
Old single-shot hunting rifles require careful handling.
single-engined (an airplane with only one engine)
あの小型機は単発なので離着陸が容易だ。
That small plane is single-engined, so takeoff and landing are easier.
one-shot; single occasion; non-serial (e.g., a one-off story, a single-episode program)
このドラマは単発のスペシャル番組として放送される。
This drama will be broadcast as a one-off special program.
単発の仕事をいくつか掛け持ちして生活している。
I make a living by juggling several one-off jobs.
あの作家は単発の短編で高い評価を受けた。
That author received high praise for a standalone short story.