(informal, often humorous) the jargon or specific vocabulary used in a particular subject or field or by a particular group of people, often strange and difficult to understand for people outside the field or group;
e.g. She used a lot of lingo when explaining her argument, which made it difficult to follow.
(noun)
(informal, often humorous) the spoken dialect that is local to a place, or broadly, a foreign language that one does not understand;
e.g. It is useful to learn some of the local lingo before visiting a new country.