no obj.
1- (of a cat) make a low continuous vibratory sound expressing contentment（猫）发呼噜声。
1.1
- (of a vehicle or machine) make such a sound when running smoothly at low speed（车辆, 机器）发出咕隆声, 咕噜咕噜响。
1.2
- no obj., with adverbial of direction(of a vehicle or engine) move smoothly while making such a sound（车辆, 发动机）咕隆咕隆地平稳转动：
a sleek blue BMW purred past him.
一辆流线型蓝色宝马轿车咕隆咕隆从他身旁驶过。
1.3
- speak in a low soft voice, especially when expressing contentment or acting seductively（尤指表达满意或引诱他人时）轻轻低语：
with direct speech 'Would you like a coffee?' she purred.“想喝杯咖啡吗？”她柔情似水地轻声问道。
- a low continuous vibratory sound, typically that made by a cat or vehicle（猫发出的）呼噜声; （车辆发出的）咕隆声, 咕噜声。
词源
early 17th cent.: imitative.