rapid increase;  proliferation;  surge;  explosion
 swiftly;  rapidly;  suddenly;  abruptly;  sharply (of a slope, bend, etc.);  steeply
 hurrying (to somewhere);  rushing;  hastening;  express (train)
 sudden;  abrupt;  rapid;  sharp;  drastic;  radical
 vital part (of the body);  tender spot;  key point;  essential point;  male crotch (as a target in fighting)
 urgent;  pressing;  immediate;  urgently;  promptly;  at once
 hurriedly;  in a hurry;  in haste; (arch.)  sudden
 sudden drop;  sharp fall;  nosedive;  swoop
 sudden turn;  sudden change;  (suddenly occurring) accident;  emergency
 sudden rise;  steep climb;  zoom;  trending
 hasty;  rash;  rushed;  hurried;  impatient;  impetuous
 sudden brake;  coming to a sudden stop
 urgency;  exigency;  emergency
 fast approach;  quick intimacy
 rapid development;  rapid unfolding
 hastily made;  improvised preparation
 emergency;  crisis;  imminent danger;  Vulnerable (conservation status);  VU
 urgent report;  urgent message
 urgent;  requiring quick (response)
 sharp turn;  tight turn;  steep turn
 (coming to a) sudden stop
 sudden change;  sudden turn
 van (of a movement);  vanguard;  forefront
 emergency case;  person that has suddenly taken ill
 sudden drop;  precipitous slope
 bursting through the surface;  suddenly surfacing;  sudden increase (e.g. in public interest);  fast rise (e.g. in rank)
 express dispatch;  urgent correspondence
 semi-express train;  local express train;  sub-express train
 abrupt turn;  sudden change
 artistic modulations in traditional Japanese performances;  opening, middle and climax (end)
 boom (development, sales, etc.)
 in no hurry;  nonessential (industry)
 sudden or unexpected disaster
 imminent danger;  impending hardship
 urgent message;  urgent dispatch;  urgent despatch
 steep sloping land;  steep terrain
 swiftly running river;  rapid stream
 emergency braking procedure (e.g. during driver training and testing)
 high fan speed (setting on air conditioner);  squall;  sudden gust