1. An organization of countries formed in 1961 to agree on a common policy for the sale of petroleum.
5. Horned vipers.
10. Thickening of tissue in the motor tracts of the lateral columns and anterior horns of the spinal cord.
13. Amino acid that is formed in the liver and converted into dopamine in the brain.
14. An oil port in southern Iraq.
15. Resinlike substance secreted by certain lac insects.
16. A prearranged fight with deadly weapons by two people (accompanied by seconds) in order to settle a quarrel over a point of honor.
17. (Babylonian) Consort of Anu.
18. (Irish) Mother of the ancient Irish gods.
19. The function or position properly or customarily occupied or served by another.
21. No longer active or practicing.
23. (pathology) An elevation of the skin filled with serous fluid.
25. Black tropical American cuckoo.
26. A small cake leavened with yeast.
29. The act of slowing down or falling behind.
31. Avatar of Vishnu.
35. A flat wing-shaped process or winglike part of an organism.
36. (informal) Exceptionally good.
38. American novelist (1909-1955).
39. (British English) A small third seat in the back of an old-fashioned two-seater.
41. Passing or able to pass air in and out of the lungs normally.
43. A trivalent metallic element of the rare earth group.
45. An associate degree in nursing.
47. The elementary stages of any subject (usually plural).
48. (electronics) Of a circuit or device having an output that is proportional to the input.
52. The face of a timepiece.
54. Powdery starch from certain sago palms.
56. Canadian hockey player (born 1948).
57. English scholastic philosopher and assumed author of Occam's Razor (1285-1349).
59. The blood group whose red cells carry both the A and B antigens.
60. Tropical American trees with palmately compound leaves and showy bell-shaped flowers.
61. The Tibeto-Burman language spoken in the Dali region of Yunnan.
62. (Judaism) A period of seven days of mourning after the death of close relative.
65. The shape of a raised edge of a more or less circular object.
66. A doctor's degree in education.
67. Small genus of Eurasian herbs.
68. The 7th letter of the Greek alphabet.

1. The probability of a specified outcome.
2. A disdainful pouting grimace.
3. A fencing sword similar to a foil but with a heavier blade.
4. West Indian tree having racemes of fragrant white flowers and yielding a durable timber and resinous juice.
5. A loose sleeveless outer garment made from aba cloth.
6. A bar of sand.
7. Standard time in the 8th time zone west of Greenwich, reckoned at the 120th meridian west.
8. A Dravidian language closely related to Tamil that is spoken in a hilly section of southwestern India.
9. Large ornamental tropical American tree with bipinnate leaves and globose clusters of flowers with crimson stamens and sweet-pulp seed pods eaten by cattle.
10. By bad luck.
11. A narrow way or road.
12. Any of a number of fishes of the family Carangidae.
20. A metric unit of volume equal to one tenth of a liter.
22. Small voraciously carnivorous freshwater fishes of South America that attack and destroy living animals.
24. A river in central Europe that arises in northwestern Czechoslovakia and flows northward through Germany to empty into the North Sea.
27. American prizefighter who won the world heavyweight championship three times (born in 1942).
28. German organist and contrapuntist (1685-1750).
30. A Gaelic-speaking Celt in Ireland or Scotland or the Isle of Man.
32. How long something has existed.
33. Japanese ornamental tree with fragrant white or pink blossoms and small yellow fruits.
34. A former agency (from 1946 to 1974) that was responsible for research into atomic energy and its peacetime uses in the United States.
37. A Russian prison camp for political prisoners.
40. Sluggish tailless Australian arboreal marsupial with gray furry ears and coat.
42. Fudge made with brown sugar and butter and milk and nuts.
44. Attack someone physically or emotionally.
46. A rechargeable battery with a nickel cathode and a cadmium anode.
47. The branch of engineering science that studies the uses of electricity and the equipment for power generation and distribution and the control of machines and communication.
49. A French river.
50. The (usually elliptical) path described by one celestial body in its revolution about another.
51. Pasture grass of plains of South America and western North America.
53. Harsh or corrosive in tone.
54. A loose sleeveless outer garment made from aba cloth.
55. A French abbot.
56. A white soft metallic element that tarnishes readily.
58. White crystalline compound used as a food additive to enhance flavor.
63. (astronomy) The angular distance of a celestial point measured westward along the celestial equator from the zenith crossing.
64. A soft white precious univalent metallic element having the highest electrical and thermal conductivity of any metal.