Speedy is a status effect conferred by various items and abilities. the effect is to increase speed by 1/2 of base speed.
For example, if my base speed was 40, with speedy I would temporarily have a speed of 60.
If my base speed was 40, and I had a +7 speed ring equipped, my speed would temporarily be 67.
Items that confer speedy
All teired Warrior's helms
Speed Sprout (obtained from forest maze and epic forest maze)
Orb of conflict
Environment can cause speedy
Speedy can also be conferred by the green pools in mad labs.