A topological space π is called semilocally simply connected iff every π₯βπ has an open neighbourhood πβπ so that every continuous loop in π is null-homotopic in π,
#m/def/topology
i.e. if π:(π,π₯)βͺ(π,π₯) is the natural inclusion then π1π:π1(π,π₯)βπ1(π,π₯) is the trivial homomorphism.