ad-lib, be caught napping, be surprised, be taken unawares, be unprepared, cook up, dash off, do offhand, fake, go off half-cocked, have no plan, improvisate, improvise, jury-rig, knock off, lash up, make up, play by ear, scrap the plan, strike off, throw off, throw together, toss off, toss out, vamp, whip up, whomp up, wing it
flash on the mind, say what comes uppermost, improvise, extemporize
, give an impetus, impel, push, start, give a start to, set going, drive, urge, boom, thrust, prod, foin, cant, elbow, shoulder, jostle, justle, hustle, hurtle, shove, jog, jolt, encounter, run against, bump against, butt against, knock one's head against, run one's head against, impinge, boost, bunt, carom, clip y, fan, fan out, jab, plug, strike, knock, hit, tap, rap, slap, flap, dab, pat, thump, beat, blow, bang, slam, dash, punch, thwack, whack, hit hard, strike hard, swap, batter, dowse, baste, pelt, patter, buffet, belabor, fetch one a blow, poke at, pink, lunge, yerk, kick, calcitrate, butt, strike at, whip, come into a collision, enter into collision, collide, sideswipe, foul, fall foul of, run foul of, telescope, throw.
be unprepared, want preparation, lack preparation, lie fallow, s'embarquer sans biscuits, live from hand to mouth, dismantle, undress, extemporize
, improvise, ad lib.