from The American Heritage® Dictionary of the English Language, 4th Edition
- Inverse; inversely: obcordate.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- Against; facing; a combining prefix found in verbs of Latin origin.
- Of a reversed shape.
- Obligatory; prepended to the name of a topic being mentioned to avoid accusations of being off-topic.
from the GNU version of the Collaborative International Dictionary of English
- A prefix signifying to, toward, before, against, reversely, etc.; also, as a simple intensive; as in oblige, to bind to; obstacle, something standing before; object, lit., to throw against; obovate, reversely, or oppositely, ovate. Ob- is commonly assimilated before c, f, g, and p, to oc-, of-, og-, and op-.
New Latin, short for obversē, obversely, from Latin obversus, past participle of obvertere, to turn toward : ob-, toward, against (from ob, toward, against, before; see epi in Indo-European roots) + vertere, to turn; see versus.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin ob. (Wiktionary)