shotgun意思是"散彈獵槍"，marriage是「婚姻」。此句意思是女方因為懷孕，面對孩子即將出世，情況緊張得如同槍對著腦袋逼不得已而締結的婚姻，指被現實所迫，不得已而結婚，即「奉子成婚」。
看看老外聊天時怎麼用a shotgun marriage：
A There are many couples who are having shotgun marriage these years.
B At least they are willing to get marry and raise their child.
A 這些年來，有不少的情侶都奉子成婚。
B 至少他們願意結婚，並撫養小孩。
a shotgun marriage例句精選：
They are going to have shotgun marriage next week.
他們下周要結婚了，是奉子成婚。
Oh buddy, the comedy recession is over. I mean, come on, talk about your shotgun marriage.
討論你覺得穩操勝券的人，嘿，老兄，喜劇已經落幕了，我的意思是說，拜託，談談你奉子成婚的事兒吧。
一方或雙方由於意外懷孕不得已而結婚。
相關：marriage made in heaven 天作之合
Brad and Cindy look so good together.The couple is the marriage made in heaven.
布萊德跟辛蒂真是絕配。這對真是天作之合。
相關：under the gun 被迫的行為
I'm going to ground you even if you are doing it under the gun.It's really a bad excuse for playing a trick to your teacher.
就算不是你的本意我也要罰你禁足。被逼迫捉弄老師實在不是個好藉口。