We establish that the infinitesimal ''H-definition'' for quasiconforma
l mappings on Carnot groups implies global quasisymmetry, and hence th
e absolute continuity on almost all lines. Our method is new even in R
(n) where we obtain that the ''limsup'' condition in the H-definition
can be replaced by a ''liminf'' condition. This leads to a new removab
ility result for (quasi)conformal mappings in Euclidean spaces. An app
lication to parametrizations of chord-are surfaces is also given.