Def a  b  T == a = b  T

is mentioned by

Thm* i:. i  0	[int_nzero_properties]
Def  == {i:| i  0 }	[int_nzero]

Try larger context: StandardLIB IF YOU CAN SEE THIS go to /sfa/Nuprl/Shared/Xindentation_hack_doc.html