I have found the term "squashed 3-sphere" used in the literature but could not locate a precise definition of it. I suppose it is topologically a 3-sphere with a metric different from the round one. Could anyone tell me what the exact definition is and or give some reference? Thanks!
EDITED: thanks for the comments. Beyond the references mentioned in (the link mentioned in) Semiclassical comment, another example is http://cds.cern.ch/record/375132/files/9812202.pdf
From the references in the comments and elesewhere it seems that the term squashed n-sphere indeed denotes a deformed (not round) metric on the n-sphere but does not have a precise meaning.