Directly or straight in front of one, as in There's the house, dead ahead. The use of dead in the sense of “straight” dates from the last quarter of the 1800s.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
How to use dead ahead in a sentence
For one breakneck moment Monday, she looked dead ahead and saw her husband surfing toward her, and then down toward the rocks.Surfer Garrett McNamara May Have Conquered His 100-Foot Wave | Andy Jacobsohn | January 31, 2013 | THE DAILY BEAST
The clouds that had been above them lay dead ahead; the ship was pointing straight upward.Astounding Stories, May, 1931 | Various
The big whistle boomed again, dead ahead, and so much nearer that it provoked the skipper to lash out a round oath.Blow The Man Down | Holman Day
But the next whistle they heard sounded dead ahead, and increased in volume of sound only gradually.Blow The Man Down | Holman Day
"You're right," said the planter, who had not observed that the strong wind would be dead ahead all the way to the anchorage.Duffels | Edward Eggleston
I headed the Warrington toward the new position, and at three A.M. picked up Wellington dead ahead.The Heroic Record of the British Navy | Archibald Hurd