This is the 13587th most frequent German word.
dickere
Comparative form of "dick" meaning "thicker."
In this sentence, 'dickere' is used as a comparative adjective to describe the thickness of the jacket in comparison to another.
Ich habe eine dickere Jacke für den Winter gekauft.
I bought a thicker jacket for the winter.
Here, 'dickere' is used to describe a line that is comparatively thicker than others on the map.
Die dickere Linie auf der Karte zeigt die Hauptstraße.
The thicker line on the map indicates the main road.
In this case, 'dickeren' is used in its accusative form as an adjective describing the requested marker, implying it's thicker than another marker.