The meaning of the Acronym SD is...

SD is

• Synchronization Directorate
• Solicitation Document
• Standby Distribution
• Sicherheits Dienst
• Special Duty
• Structured Design
• Super-Dreadnought

More Meanings For SD:

• Selective Default
• Saving the Data
• Secure Digital
• Sound ( Entropic Sound Data format)
• Submitted Data
• SCSI Disk
• Single Data
• Sorted Directory
• Spool Directory
• Scattered Disk
• Semi Discrete
• SCSI Device
• SAN (Storage Area Network) Disk
• Spin Down
• Scan Disk

SD is also in:

• Assembly
• Databases
• Drivers
• File Extensions
• General
• Hardware