A useful umbrella term describing the Circle, Hammersmith & City and Metropolitan lines' shared route between Baker Street and Aldgate.

On London Underground maps these lines are individually colour-coded yellow, pink and magenta. When viewed side-by-side the lines resemble Neapolitan ice cream, albeit with the Metropolitan line's dark magenta replacing Neapolitan ice cream's chocolate brown.
Example 1:
"How do I get from Liverpool Street to Farringdon?"
"Any of the Neapolitan lines will do"

Example 2:
"What lines pass through Baker Street?"
"The Bakerloo, Jubilee and Neapolitan lines"
by LandinInnit September 1, 2013
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Any combination of narcotics mixed for insufflation.
I've got some ket left, let's add it to the coke and mandy and make some Neapolitan Lines.
by El_Bosco May 19, 2022
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