1610s, from French rétroactif (16c.) "casting or relating back," from Latin retroact-, past participle stem of retroagere "drive or turn back," from retro- "back" (see retro-) + agere "to drive, set in motion" (see act (v.)). Related: Retroactively.
实用例句
1. The seagulls swirled in aerial combat over the barges.
海鸥盘旋在驳船上方，展开空中的搏斗。来自柯林斯例句
2. a flock of seagulls
一群海鸥来自《权威词典》
3. Seagulls followed in the wake of the huge ship.
海鸥尾随于大船之后.来自《简明英汉词典》
4. The seagulls were wheeling in the air above the ship.
