der Abschuss
shootdown
The hitting and destroying of a flying object, especially an aircraft or a missile, with a weapon.
Der Abschuss der feindlichen Drohne wurde vom Kommando bestätigt.
The shootdown of the enemy drone was confirmed by command.

shootdown / killing / rejection
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shootdown
The hitting and destroying of a flying object, especially an aircraft or a missile, with a weapon.
Der Abschuss der feindlichen Drohne wurde vom Kommando bestätigt.
The shootdown of the enemy drone was confirmed by command.

'Der Abschuss' (shootdown / killing / rejection) is the noun for the separable verb 'abschießen' (to shoot down / to shoot). The verb means to hit something with a shot, bring it down, or kill it.
Der Soldat hat befohlen, die Rakete abzuschießen.
The soldier ordered them to shoot down the missile.
You can recognize the meaning from the topic: in a military context, it is about flying objects; in a hunting context, about animals; and in a social, colloquial context, about a rejection.
Der Abschuss des Satelliten wurde weltweit kritisiert.
The shootdown of the satellite was criticized worldwide.
The meaning 'rebuff' or 'rejection' is strongly colloquial. Use this expression only in informal conversations with friends.
Ich habe versucht, sie nach einem Date zu fragen, aber ich habe mir einen totalen Abschuss geholt.
I tried to ask her out on a date, but I got totally rejected.
In the colloquial meaning, the fixed expression 'sich einen Abschuss holen' (to get rejected) is almost always used. The person who is rejected is the subject of the sentence.
Er hat auf der Party bei drei verschiedenen Frauen versucht zu flirten und hat sich jedes Mal einen Abschuss geholt.
At the party, he tried to flirt with three different women and got rejected every time.
hit
'der Treffer' and 'der Abschuss' can both have to do with a successful shot. 'Treffer' only means that a shot, strike, or thrust reaches its target. The target does not have to be destroyed. 'Abschuss' is more specific: a flying object is hit and destroyed with a weapon, or a wild animal is killed while hunting. Learners may confuse the words because a shootdown always involves a hit. But not every 'Treffer' is an 'Abschuss'.

Der Abschuss der Drohne wurde später von der Armee bestätigt.
The shootdown of the drone was later confirmed by the army.
Der letzte Schuss war ein Treffer, aber das Ziel blieb ganz.
The last shot was a hit, but the target remained intact.