strain 1 
(strān)
(strān)v. strained, strain·ing, strains
v.tr.
1.
a. To pull, draw, or stretch tight: The heavy load strained the rope.
b. Physics To cause distortion of (a body's parts or shape) by applying an external force; deform.
2. To exert, use, or tax to the utmost: straining our ears to hear.
3. To injure or impair by overuse or overexertion; wrench: strain a muscle.
4. To damage or weaken by pressure or tension: winds that strained the mast.
5. To force beyond the proper or reasonable limit: an excuse that strains credulity.
6.
a. To pass (a liquid) through a filtering agent such as a strainer.
b. To draw off or remove by filtration: strained the pulp from the juice.
7. Archaic To embrace or clasp tightly; hug.
v.intr.
1.
a. To make strong or steady efforts; strive hard: straining to complete the coursework.
b. To contract or exert one's muscles to the utmost.
2. To pull or push forcibly or violently: The dog strained at its leash.
3. To be or become wrenched or twisted: the flagpole straining in the wind.
4. To be subjected to great stress: With such busy lives, the marriage can strain.
5. To pass through a filtering agent: The muddy water strains slowly.
n.
Idiom: 1.
a. The act of straining.
b. The state of being strained: the strain on the cable.
2.
a. Extreme or laborious effort, exertion, or work: moved the sofa with little strain.
b. A great or excessive demand or stress on one's body, mind, or resources: the strain of managing both a family and a career.
c. The state of being subjected to such demands or stresses: trying to work under great strain.
3. A wrench, twist, or other physical injury resulting from excessive tension, effort, or use.
4. Physics Any of several kinds of deformation of the dimensions of a body when subjected to stress, as axial strain or elastic strain.
5. An exceptional degree or pitch: a strain of zealous idealism.
strain at stool
To have difficulty defecating.
[Middle English streinen, from Old French estreindre, estrein-, to bind tightly, from Latin stringere; see streig- in the Appendix of Indo-European roots.]