Altair Engineering Inc. filed SEC Form 8-K: Entry into a Material Definitive Agreement, Termination of a Material Definitive Agreement, Material Modification to Rights of Security Holders, Changes in Control of Registrant, Leadership Update, Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Completion of Acquisition or Disposition of Assets, Events That Accelerate or Increase a Direct Financial Obligation, Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing