zero in on

[zero in on] {v.} 1. To adjust a gun so that it will exactly hit (atarget); aim at.

Big guns were zeroed in on the enemy fort.

American missiles have been zeroed in on certain targets, to be firedif necessary.

2. {slang} To give your full attention to.

TheSenate zeroed in on the Latin-American problems.

Let's zero in ongrammar tonight.