isocline

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Geology An anticline or syncline so tightly folded that the rock beds of the two sides are nearly parallel.

Century Dictionary and Cyclopedia

1. n. 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.

Wiktionary

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