default on (v.+prep.)
▲default on sth
1.拖欠…fail to pay (a debt)
He defaulted on his payments for support of the child.他拖欠孩子的抚养费。
The country has defaulted on its foreign debts.那个国家拖欠了外债。
2.未出席…did not arrive
He defaulted on the rehearsal.他在排练时没有到场。

用作不及物动词
▲S+～(+A)
He defaulted in his payments on the loan.他没有按期偿还贷款。
He defaulted in the wrestling tournament.他在摔跤比赛中弃权了。

in default of
在缺少…的情况下because of the absence or lack of
In default of experts' help,we shall have to rely on our own efforts.没有专家的帮助，我们将只得依靠自己的力量。

The defendant made default yesterday.被告昨天未到庭。
A total of 125 contracts went into default up to May 25.至5月25日,共有125份合同未履行。
His car was repossessed because of default of monthly installment.因为拖欠按月应付的分期付款,他的汽车被收回了。
He lost the world title by default.他由于弃权而失去了世界冠军的称号。

［词源］＜古法语defaute(缺,失败)