reluctance

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

• noun The state of being reluctant; unwillingness.
• noun Physics A measure of the opposition to magnetic flux, analogous to electric resistance.

from The Century Dictionary.

• noun In electricity, the resistance to magnetic flux: the reciprocal of permeance. The unit of reluctance is the oersted, which is the reluctance of a magnetic circuit in which a unit of magnetomotive force will produce unit flux.
• noun The state of being reluctant; aversion; repugnance; unwillingness: often followed by to, sometimes by against.
• noun Synonyms Hatred, Dislike (see antipathy), backwardness, disinclination. See list under aversion.

from the GNU version of the Collaborative International Dictionary of English.

• noun The state or quality of being reluctant; repugnance; aversion of mind; unwillingness; -- often followed by an infinitive, or by to and a noun, formerly sometimes by against.
• noun (Elec.) Magnetic resistance, being equal to the ratio of magnetomotive force to magnetic flux.

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

• noun Unwillingness to do something.
• noun Hesitancy in taking some action.
• noun physics That property of a magnetic circuit analogous to resistance in an electric circuit.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a certain degree of unwillingness
• noun (physics) opposition to magnetic flux (analogous to electric resistance)