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tangent

1 ENTRIES FOUND:
tangent /ˈtænʤənt/ noun
plural tangents
tangent
/ˈtænʤənt/
noun
plural tangents
Britannica Dictionary definition of TANGENT
[count] geometry
: a line that touches a sphere or circle at only one point

go off on a tangent

(US) or British go off at a tangent
: to start talking about something that is only slightly or indirectly related to the original subject