der Arsch
ass
A vulgar term for the human buttocks.
Er ist beim Skaten hingefallen und direkt auf den Arsch geknallt.
He fell while skating and landed right on his ass.

ass / asshole
Loading your saved state.
ass
A vulgar term for the human buttocks.
Er ist beim Skaten hingefallen und direkt auf den Arsch geknallt.
He fell while skating and landed right on his ass.

The word 'Arsch' (ass) is vulgar and belongs to colloquial language. It should absolutely be avoided in formal or polite situations, as it is perceived as very rude or insulting.
Pass auf, was du sagst, hier sind Kinder dabei!
Watch what you say, there are children here!
When referring to the buttocks, the preposition 'auf' (on) is often used. The accusative indicates movement ('auf den Arsch fallen' = to fall on one's ass), while the dative describes a state or location ('auf dem Arsch sitzen' = to sit on one's ass).
Ich bin auf dem nassen Boden ausgerutscht und auf den Arsch gefallen.
I slipped on the wet floor and fell on my ass.
As an insult for a person, 'Arsch' (asshole) is often used with an indefinite article or an intensifier like 'so ein' (such a). It describes a person whose behavior is perceived as unfair or mean.
Er hat mir nicht geholfen, obwohl er es versprochen hat. So ein Arsch!
He didn't help me even though he promised. What an asshole!
The idiom 'am Arsch der Welt' (in the middle of nowhere) is a fixed unit. It is used to describe a place as extremely remote and isolated.
Mein neues Büro ist in einem Industriegebiet am Arsch der Welt.
My new office is in an industrial area in the middle of nowhere.
The expression 'am Arsch sein' (to be screwed / exhausted) is a fixed unit. It means that someone is completely exhausted, financially ruined, or in a hopeless situation.
Nach dem Marathon war ich körperlich total am Arsch.
After the marathon, I was physically totally exhausted.
The demand 'den Arsch hochkriegen' (to get off one's ass) is a fixed expression. The object 'den Arsch' is always in the accusative.
Wenn du die Prüfung bestehen willst, musst du endlich den Arsch hochkriegen und lernen.
If you want to pass the exam, you finally have to get off your ass and study.
In the expression 'jemandem in den Arsch kriechen' (to kiss someone's ass), the person one wants to ingratiate oneself with is always in the dative. It is a very vulgar description of submissive behavior.
Er kriecht dem Professor in den Arsch, um eine bessere Note zu bekommen.
He kisses the professor's ass to get a better grade.
The exclamation 'Leck mich am Arsch!' (Kiss my ass!) is a fixed, very crude idiom. It is used to reject someone sharply or to express that you don't care about something at all.
Er wollte, dass ich seine Arbeit mache. Ich sagte ihm, er könne mich am Arsch lecken.
He wanted me to do his work. I told him he could kiss my ass.
asshole
'der Arsch' and 'das Arschloch' are both very vulgar words and can be used as crude insults. As insults, they are similar, but 'Arschloch' often sounds stronger and more directly aimed at a person. For the body, the difference is important: 'Arsch' means the buttocks, while 'Arschloch' means the anus. Learners may confuse the words because both are vulgar and both have to do with the body part. In polite situations, you should avoid both words.

Nach dem langen Radfahren tat ihm der Arsch weh.
After the long bike ride, his ass hurt.
Nach dem Streit nannte Tom den anderen ein Arschloch.
After the argument, Tom called the other person an asshole.