1. The outermost of the perforations which make up the foramen of the ovule of a plant.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• wxostome,
• sxostome,
• dxostome,
• rxostome,
• 4xostome,
• 3xostome,
• ezostome,
• ecostome,
• esostome,
• exkstome,
• exlstome,
• exostom,
• exosotme,
• exostomme,
• exostomee,
• Exostoma,
• Eksostome,
• Exastome,
• Exostomey,
• Exestome

The plural of the "Exostome" can be the "exostomes".

The singular of the "Exostome" can be the "Exostome".