adverbThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
At once; immediately: discovered straight off that the furnace wasn't working.
straight off - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Also, straight away. Immediately, as in I knew straight off that he was lying, or I'll get to the dishes straight away. The first term dates from the late 1700s, the variant from the mid-1600s.