isocline

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An anticline or syncline so tightly folded that the rock beds of the two sides are nearly parallel.

from The Century Dictionary.

• noun In geology, a fold in which the strata are so appressed that the limbs or flanks (the parts on each side of the axis of the fold) are isoclinal, or dip in the same direction. See monocline. Also called overturn, or overturned anticlinal.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun geology A tightly folded syncline or anticline in which the two sides are almost parallel
• noun mathematics Any of a series of lines having the same slope
• noun A line on a map linking places with the same magnetic dip