Theme: Six Packs - The start of each six theme answer can precede "pack".
17A. Completely dark : JET-BLACK. Jet pack.
21A. Getting-to-know-you party activity : ICEBREAKER. Ice pack.
26A. Dirty fighting? : MUD-WRESTLING. Mud pack.
39A. Wearisome routine : RAT RACE. Rat pack.
47A. "Wow, she's good-looking!" sounds : WOLF WHISTLES. Wolf pack.
58A. "Funny Girl" leading role : FANNY BRICE. Fanny pack.
66A. Some sculpted abs ... and what the starts of 17-, 21-, 26-, 39-, 47- and 58-Across are altogether? : SIX PACKS
Argyle here. One of the first things I noticed was that the grid resembled a labyrinth but I didn't get lost. Strong theme. The fill has a strong Middle-Eastern influence with a smattering of foreign words from around the world.
Across:
1. Lea low : "MOO". Cute alliteration.
4. Rocket interceptors, briefly : ABMs. Anti-Ballistic Missile.
8. Doesn't tip : STIFFS. The bane of waitstaffs everywhere.
14. DJ's array : CDs
15. Atahualpa, notably : INCA. He was the last sovereign emperor of the Inca Empire.
16. Sci-fi author __ K. Le Guin : URSULA. She wrote the Earthsea fantasy novels. The Margaret Mead of science-fiction?
19. Took an intersecting road : TURNED. Thought of Robert Frost, did you?
20. It's not butter : OLEO
23. Soft baseball hit : BLOOP
25. Facility : EASE
33. "Weeds" airer, in TV listings : SHO. Showtime, a premium television network.
36. Latvian capital : RIGA. Here.
37. Eastern principle : TAO
38. Liven (up) : PEP
43. Expressive rock genre : EMO. Short for emotional rock music.
44. __ of Good Feelings : ERA. The Era of Good Feelings was the name applied to the period in the United States corresponding with the term of President James Monroe. It lasted approximately from 1816 to 1824.
45. "Zounds!" : "EGAD!"
46. Old boys? : MEN
53. Wrath, in a classic hymn : IRAE. "Dies Irae" ("Day of Wrath").
54. Fat cat : NABOB. Originally, a governor in India under the Mogul Empire. Also called nawab.
64. Quayle's successor : GORE
65. Orbital extreme : APOGEE
68. Mother with a Nobel prize : TERESA. Missionary in Calcutta.
69. Depilatory brand : NAIR
70. AFL partner : CIO. The American Federation of Labor and Congress of Industrial Organizations.
71. Turns over, as an engine : STARTS. But they don't start, sometimes!
72. Film pooch in a tornado : TOTO. "The Wizard of Oz".
73. Tolkien tree creature : ENT
Down:
1. Low-paying position : McJOB
2. Nancy who's slated to replace Mary Hart on "Entertainment Tonight" : O'DELL. Image.
3. Bone: Pref. : OSTEO
4. Have a bug : AIL
5. __ B'rith : B'NAI
6. Cornerstone 1300 : MCCC
7. Benefit : SAKE
8. Hindu aphorisms : SUTRAs. An aphorism is a terse saying embodying a general truth, or astute observation.
9. Most loyal : TRUEST
10. Its anthem is "Hatikvah" : ISRAEL. Clip (3:11) with lyrics.
11. Wagnalls's partner : FUNK. They published encyclopedias.
12. Make a run for it : FLEE
13. 1980-81 Iranian president Bani-__ : SADR. Image
18. Bust's opposite : BOOM
22. Spelling contest : BEE
24. Music to a cat lover's ears : PURR
27. Day in Durango : DIA. Down Mexico way.
28. Lb. or oz. : WGT.
29. Filet mignon requests : RAREs
30. Couple in People : ITEM. People Magazine.
31. Tom, Dick or Harry : NAME
32. Continue : GO ON
33. Eject, as lava : SPEW
34. Medal recipient : HERO
35. Stone for many Libras : OPAL
40. Rep. with a cut : AGT.. Agent.
41. Berkeley school, familiarly : CAL. University of California, Berkeley.
42. First lady's home? : EDEN
48. Identify, as a perp : FINGER
49. Most ironic : WRYEST
50. __ corpus : HABEAS
51. Suffix with hotel : IER
52. "Beowulf" or "Star Wars" : SAGA
55. Bologna ball game : BOCCE. Italian origin.
56. Pest control name : ORKIN
57. Stupefy with drink : BESOT
58. Pool legend Minnesota __ : FATS. The pool that requires a cue.
59. In __: peeved : A PET
60. Director Ephron : NORA. Film director, producer, screenwriter, novelist, journalist, author, and blogger. Keeps busy, eh?
61. Fails to be : ISN'T
62. Giovanni's good-bye : CIAO. Italian.
63. Stage direction : EXIT
67. Tour golfer : PRO
Argyle