Although not strictly what you want, the closest built in feature I can think of in Mac OS is the Word Completion feature. Press Escape while you're in the middle of typing a word and it'll bring up all the suggestions of what it thinks you're trying to type. For certain apps Escape won't work and you'll have to use Option-Escape. Note this only works in Cocoa apps such as TextEdit.
Damn, this is the one feature (along with inactive scrolling) that I miss the most when using Windows. It was so useful when I wasn't sure about the spelling of a particular word and I used to use it all the time when writing in these forums!