The acrosomal membrane region that underlies the plasma membrane of the sperm. This membrane fuses with the sperm plasma membrane as part of the acrosome reaction.
Source:
GOC:dph,
PMID:8936405
Comment
Note that this term is not a descendant of 'organelle outer membrane ; GO:0031968' because the outer acrosomal membrane is a portion of the acrosomal membrane; the latter is a single lipid bilayer.