From Longman Dictionary of Contemporary Englishfirst thingfirst thingEARLYas soon as you get up in the morning, or as soon as you start work I’ll call you first thing tomorrow. We’re leaving first thing. → first
Examples from the Corpus
first thing• I'll telephone her first thing, I promise.• The first thing I saw when my eyes blinked into focus was an ant marching over a small stone.• I'll call her first thing in the morning.• Double advanced mathematics first thing in the morning.• What is the last recollection before losing consciousness and the first thing recalled after regaining awareness?• The first things that were provided were pubs and working men's clubs.• The first thing to do is make sure the doors themselves are strong enough.• In this case, the first thing to go was his appetite.• I will go to see Ken Hurren first thing tomorrow morning and tell him that Summerchild was working on defence.• Leave it on my desk and I'll deal with it first thing tomorrow.• Sharon wants that report on her desk first thing tomorrow.first thingfirst thingBEGINNINGat the beginning of a day, morning, afternoon etc Jean liked to go for a swim first thing in the morning. → thingExamples from the Corpus
first thing in the morning• Why not set a few moments aside first thing in the morning and last thing at night?• The owls are often seen outside the barn first thing in the morning, and they nip into the hay when disturbed.• They brought her before a magistrate the first thing in the morning.• They all go through first thing in the morning.• Alendronate must be taken only with a full glass of plain water, first thing in the morning on an empty stomach. 