The words disruptor and disrupter are very similar to the words adaptor and adapter. You may even feel it is easy to then guess which is the primary spelling. The Australian Oxford Dictionary and the Macquarie Oxford Dictionary both agree the primary spelling is disrupter and the secondary spelling is disruptor.

A: Dictionaries give “disrupter” as the usual spelling, but some do give “disruptor” as an acceptable variant. You can find the variant spelling in the Oxford English Dictionary as well as Merriam Webster’s Unabridged, The American Heritage Dictionary of the English Language (5th ed.), and the Collins English Dictionary online.