the GNU version of the Collaborative International Dictionary of English
adj. Giving previous warning or notice.
The Century Dictionary and Cyclopedia
Giving premonition; serving to warn or notify beforehand.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. warning of future misfortune
Word Usage
"Scientists have long known about this so-called premonitory phase, which occurs well before the better-known aura, the flashing lights and wavy lines that about 30% of migraine sufferers see shortly before the headache begins."