settle down phrasal verb (see also settle)

1. settle (somebody) down to become quiet and calm, or to make someone quiet and calm:
Shh! Settle down, please! Now turn to page 57.
When Kyle was a baby, we used to take him for rides in the car to settle him down.

2. to start living a quiet and calm life in one place, especially when you get married:
They’d like to see their daughter settle down, get married, and have kids.

3. to start giving all of your attention to a job or activity
settle down to
I sorted out my mail, then settled down to some serious work.

4. if a situation settles down, it becomes calmer and you are less busy or less worried:
It’s been really hectic here. When things settle down, I’ll give you a call.

[TahlilGaran] Dictionary of Contemporary English ▲

settle down
settle (someone) down
to get someone to behave more calmly.
He was so upset that one of his brothers had to settle him down.

Usage notes: often used as an order:
OK, class, settle down.

to accept responsibilities and behave in a more regular way than you have in the past.
Larry met his wife in San Antonio, where they have settled down and started a family.

[TahlilGaran] English Idioms Dictionary ▲

settle down
1. establish a regular routine after getting married
After dating dozens of women the young man finally decided to settle down.

2. to begin to live a quiet/stable life
My friend settled down and started a family after he finished university.

3. to calm down
The baby finally settled down and went to sleep.

[TahlilGaran] English Idioms Dictionary ▲

settle down
v.
1. To live more quietly and sensibly; have a regular place to live and a regular job; stop acting wildly or carelessly, especially by growing up.
John will settle down after he gets a job and gets married.
2. To become quiet, calm, or comfortable.
Father settled down with the newspaper.
The house settled down for the night after the children were put to bed.
The teacher told the students to settle down and study the lesson.

[TahlilGaran] English Idioms Dictionary ▲

settle someone down
settle (someone) down
to get someone to behave more calmly.
He was so upset that one of his brothers had to settle him down.

Usage notes: often used as an order:
OK, class, settle down.

to accept responsibilities and behave in a more regular way than you have in the past.
Larry met his wife in San Antonio, where they have settled down and started a family.

[TahlilGaran] English Idioms Dictionary ▲