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[inner city]  {n.},  {colloquial}

Densely populated neighborhoods in large metropolitan areas inhabited by low income families usually of minority backgrounds, such as Mexicans, Puerto Ricans, or African Americans; characterized by slums and  […]

[in nothing flat]

See: [IN NO TIME].

[in no time] or [in nothing flat]  {adv. phr.},  {informal}

In a very little time; soon; quickly.

When the entire class worked together they finished the project in no time.

[in no uncertain terms]

See: [IN SO MANY WORDS] (2).

[in on]  {prep.}

1. Joining together for.

The children collected money from their classmates and went in on a present for their teacher.

2. Told about; having knowledge of.

Bob was in on the secret.

* /The other girls wouldn't let Mary in on  […]

[in one ear and out the other]

See: [GO IN ONE EAR AND OUT THE OTHER].

[in one fell swoop] or [at one fell swoop]  {adv. phr.}

1.  {literary}

In one attack or accident; in one bad blow.

The millionaire lost his money and his friends at one fell swoop.

2. At one time; at the same time.

* /Three cars drove into the  […]

[in one's bad graces]  {adj. phr.}

Not approved by; not liked by.

John was in his mother's bad graces because he spilled his milk on the tablecloth.

Don got in the bad graces of the teacher by laughing at her hat.

Compare: [DOWN ON], [IN BAD],  […]

[in one's behalf] or [on one's behalf]  {adv. phr.},  {informal}

1. For someone else; in your place.

My husband could not be here tonight, but I want to thank you on his behalf.

2. For the good of another person or group; as a help to someone.

*  […]

[in one's blood] or [into one's blood]  {adv. phr.}

Agreeing perfectly with one's sympathies, feelings, and desires.

Living in a warm section of the country gets in your blood.

The woods got into Jim's blood.

Contrast: [OUT OF ONE'S BLOOD].