die Radfahrerin
female cyclist
A female person who rides a bicycle.
Eine Radfahrerin mit Helm überholte uns auf dem Radweg.
A female cyclist wearing a helmet passed us on the bike path.

female cyclist
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female cyclist
A female person who rides a bicycle.
Eine Radfahrerin mit Helm überholte uns auf dem Radweg.
A female cyclist wearing a helmet passed us on the bike path.

The word is derived from the verb 'Rad fahren' (to ride a bike). The ending '-in' is the typical German ending used to refer to a female person who performs a certain activity.
Als Kind war sie eine begeisterte Radfahrerin.
As a child, she was an enthusiastic cyclist.
The noun 'die Radfahrerin' (female cyclist) describes a person who performs the activity 'Rad fahren' (to ride a bike). Note that the verb is written as two words.
Die Radfahrerin musste an der Ampel anhalten.
The female cyclist had to stop at the traffic light.
In everyday language, 'Radfahrerin' (female cyclist) is often combined with verbs from road traffic, for example 'eine Radfahrerin wird übersehen' (a female cyclist is overlooked), 'eine Radfahrerin biegt ab' (a female cyclist turns), or 'eine Radfahrerin stürzt' (a female cyclist falls).
An der Kreuzung wurde eine Radfahrerin von einem Auto übersehen.
At the intersection, a female cyclist was overlooked by a car.
cyclist
'der Radfahrer' and 'die Radfahrerin' both refer to a person who rides a bicycle. The difference is grammatical gender and usually also the person being referred to: 'der Radfahrer' means a male cyclist, while 'die Radfahrerin' means a female cyclist. The words are easy to confuse because they look almost the same and only the ending is different. Pay special attention to the article: 'der' with 'Radfahrer', 'die' with 'Radfahrerin'.

Wegen des starken Windes fährt die Radfahrerin heute langsamer.
Because of the strong wind, the female cyclist is riding more slowly today.
Der Radfahrer wartet an der roten Ampel.
The cyclist is waiting at the red traffic light.