A defense unit is a unit that defends nearby units by absorbing or redirecting damage. These include shield generators and walls. Some units are dedicated to generating shields. There are such as the Asylum, Parashield , bulwark and shield generating structures such as the T2 shield generator. A few other units are capable of projecting shields, including an upgraded UEF ACU and the Fatboy. Note that units like the Titan and the Obsidian are not considered defense units because their shields only protect themselves, not nearby units. The deceiver and CI:18 Mermaid are also defense units, as they hide units from radar.
For a list of all defense units, see the defense units category.