dart:
n. 飞镖；急驰，飞奔；一阵剧痛；（衣服的）褶；热带和亚热带鱼类
v. 急冲，飞奔；投掷，投射；把（目光）飞快扫向
The dart cannot feed itself.
飞镖无法自食其力。
She made a dart for the door.
她朝门口冲去。
Nina felt a sudden dart of panic.
尼娜突然感到一阵恐慌。
Car horns toot as cyclists dart precariously through the traffic.
当骑车人冒失地穿过车流时，汽车喇叭响个不停。
flutter:
v. 飘动；（鸟或昆虫）鼓翼；飞来飞去；（心脏等）怦怦乱跳；（人）奔忙
n. 振动；（非正式）小赌注；紧张兴奋；（心脏的）怦怦乱跳；扑动；（重放录音的）颤振
The sparrow fluttered its wings and flew away from the windowsill.
麻雀振翅飞离窗台。
Flags are fluttering in the breeze.
旗帜在微风中飘扬。
Her heart gave a flutter when she saw him.
她见到他时心怦怦乱跳。
The sound of his voice in the hall made her heart flutter.
他在大厅中讲话的声音使她的心怦怦直跳。
意思上的区别：
dart 是发射，急冲的意思
flutter 是抖动，震动的意思
