Permafrost is a status effect characterized as an attack slowing bloons through limited layers, but lasts indefinitely. It was introduced in Bloons TD 3 with introduction of the Ice Tower's Permafrost upgrade, and later in Bloons TD 6 with the same upgrade. It is part of the damage types family.
Permafrost slowdown is represented on the Bloons Wiki as 
, the upgrade icon for Permafrost in Bloons TD 6, as this is the only upgrade that does this.
Permafrost is a subset of Slowdown 
, as they both slowdown bloons so their movement is less than 100% but more than 0%. Permafrost specifically lasts permamently, unless a layer affected by this effect is popped. In Bloons TD 6, only Tier 5 Ice Monkeys can apply Permafrost to MOAB-Class Bloons.
