Толковый словарь английского языка Oxford English Reference - ob-

prefix (also oc- before c, of- before f, op- before p) occurring mainly in words of Latin origin, meaning: 1 exposure, openness (object; obverse). 2 meeting or facing (occasion; obvious). 3 direction (oblong; offer). 4 opposition, hostility, or resistance (obstreperous; opponent; obstinate). 5 hindrance, blocking, or concealment (obese; obstacle; occult). 6 finality or completeness (obsolete; occupy). 7 (in modern technical words) inversely; in a direction or manner contrary to the usual (obconical; obovate). Etymology: L f. ob towards, against, in the way of