The formation of a spore following the marked enlargement of part of a cell before separation by a septum. Blastospores are a type of asexual spore found in some fungi, most notably the class Glomeromycota.
Source:
GOC:mah,
https://en.wikipedia.org/wiki/Blastospore
Comment
Note that this term should not be confused with the usage of 'blastospore' to mean any yeast-form fungal cell, as in Candida species.