der Rückruf
callback
A phone call to someone who previously tried to reach you.
Ich habe Ihren Anruf verpasst, aber ich verspreche Ihnen einen Rückruf bis heute Abend.
I missed your call, but I promise you a callback by this evening.

callback / recall
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callback
A phone call to someone who previously tried to reach you.
Ich habe Ihren Anruf verpasst, aber ich verspreche Ihnen einen Rückruf bis heute Abend.
I missed your call, but I promise you a callback by this evening.

The word is made up of 'Rück-' (from 'zurück', back) and 'Ruf' (from 'rufen', to call). So it literally means a 'call back', which fits all meanings.
Ich warte dringend auf einen Rückruf von meinem Arzt.
I am urgently waiting for a callback from my doctor.
The noun 'der Rückruf' (callback/recall) is derived directly from the separable verb 'zurückrufen' (to call back/recall). You can 'jemanden zurückrufen' (call someone back), 'ein Produkt zurückrufen' (recall a product) as a manufacturer, or 'einen Diplomaten zurückrufen' (recall a diplomat) as a government.
Der Autohersteller musste Tausende Fahrzeuge zurückrufen.
The car manufacturer had to recall thousands of vehicles.
The context makes clear which meaning is intended. If it is about telephoning, it is a call. If it is about products and companies, it is a product return/recall. If it is about politics or the military, it is the recall of a person.
Wegen eines Defekts gab es einen Rückruf für das Kinderspielzeug.
Because of a defect, there was a recall for the children's toy.
In the telephone context, fixed phrases such as 'um einen Rückruf bitten' (to ask for a callback), 'einen Rückruf erhalten' (to receive a callback), or 'einen Rückruf zusagen' (to promise a callback) are very common.
Könnten Sie Herrn Meier bitte um einen Rückruf bitten?
Could you please ask Mr. Meier to call back?
With product returns, people often say that a manufacturer 'einen Rückruf startet' (launches a recall) or that customers 'von einem Rückruf betroffen sind' (are affected by a recall).
Alle Kunden, die von dem Rückruf betroffen sind, erhalten eine E-Mail.
All customers affected by the recall will receive an email.
This meaning is used almost exclusively in formal, official contexts such as news or political reports. It usually concerns diplomats, ambassadors, or soldiers.
Die Regierung ordnete den sofortigen Rückruf aller im Ausland stationierten Experten an.
The government ordered the immediate recall of all experts stationed abroad.
call
'Anruf' and 'Rückruf' both have to do with the phone, but they do not describe the same situation. An 'Anruf' is general: someone calls another person. A 'Rückruf' happens in response to an earlier call or message. So you call back because someone previously tried to reach you. The risk of confusion is high because a 'Rückruf' is also an 'Anruf'. More precisely: every 'Rückruf' is an 'Anruf', but not every 'Anruf' is a 'Rückruf'.

Nach dem Unterricht hat die Ärztin um einen Rückruf gebeten.
After the lesson, the doctor asked for a callback.
Der Anruf von meiner Schwester kam mitten im Meeting.
The call from my sister came right in the middle of the meeting.