According to Literary Terms and Definitions, masculine and feminine endings are defined as:
masculine: If a line ends in a standard iamb, with a final stressed syllable, it is said to have a masculine ending.
feminine: If a line ends in a lightly stressed syllable, it is said to be feminine.
With regard to Shakespeare's play, Macbeth, Act I, scene vii, I have provided examples of each, based upon the definitions above.
A feminine line ending (unstressed) is found in the following hypercatalectic (hypercatalectic: extra unstressed beat) quotation:
We'd jump' / the life' / to come'. / But in' / these cas' / -es~... (7)
Stress is found as follows: jump, life, come, in, cas-.
The line contains five stressed feet as shown by the five stressed words. The -es of "cases" is the extra hypercatalectic syllable of the line and it is unstressed, making this a feminine line. Iambic pentameter, Shakespeare's favored form of writing, stresses beats as one unstressed followed by one stressed beat: syllable counts can be misleading because of elision and pauses.
Another feminine unstressed line ending is found in the following quote:
It were' / done quick' / -ly. If_the' / as -sas' / -si -na' / tion~ (2)
Stress is found as follows: were, quick-, if_the, -sas-, -na-. The words "if" and "the" are elided to form one beat. According to dictionaries, "assassination" can only be stressed asSASsiNAtion.
The best way to calculate meter is to scan the beat: Some students clap the beat out, some count beats on their fingers. If I get stumped--and these two lines are tough because the words used contain multiple syllables--I use a pencil and put a stress mark over syllables that must, according to dictionary entries, carry stress and work from there.
A masculine ending is:
~ Blood_y' / in -struc_tions', / which, be' / -ing taught', / re -turn'... (9)
Stress is found as follows: blood_y, -struc_tions, be-, taught, -turn. This is a difficult one because it has both a headless (headless: acephalus) first foot, with an elision between the two syllables of "bloody," followed by a second elision in "instruc_tion" between the 2nd and 3rd syllables. "Return" must be stressed on the last syllable, making this a masculine line.
Another feminine ending is:
Of his' / own cham' / -ber_and used' / their ve' / -ry dag' / -gers~ (76)
"Chamber" must be stressed on cham- and "daggers" must be stressed on dag-, so they determine the line stress. There is also an elision between "-ber" and "and" that makes one beat. Stress is found as follows: his, cham-, used, ve-, dag-. That leaves -gers as an extra unstressed syllable in a hypercatalectic feminine line.
It would appear that in this scene, there are more regular iambic masculine endings than hypercatalectic feminine endings. Feminine endings will always have an unstressed final beat as in these hypercatalectic iambs or as in regular trochees and regular dactyls, and masculine endings will always have a stressed final beat as in regular iambs and anapests or as in catalectic trochees and catalectic dactyls (catalexis: adding or omitting final or beginning unstressed syllables).