The definition is written out in the final section of the linked page. These were originally separate blog posts, so I assume the author got some feedback on this and decided to spell it out finally.
Working on compilers, SOA to me means "Struct Of Arrays", which is a data layout format that is much more amenable to vector or GPU code than the "Array of Structs" representation that languages tend to guide you to implementing.
As far as I know, SOA means "safe operating area", and I have no idea how the hell this pertains to anything they're discussing.
Google tells me SOA probably means "service oriented architecture" (or the "society of actuaries"), but geez.