ecthlipsis

1. The omission or elision of letters or syllables (often the consonant "m" and the vowel that precedes it) for the sake of poetical meter. A kind of metaplasm specific to Latin. (Silva Rhetoricae)

2. a striking out: a Grammatical figure when the letter M, with his vowel is taken away, the next word beginning with a vowel.; Ecthlipsis, elisio, a striking out. It is a figure of Prosodia, especially when (M) with his vowel is taken away, the next word beginning with a vowel. (JG Smith)

3. Elision is the running together of two syllables into one by the dropping of one or more letters. This may sometimes be necessary in English verse, but some of the best critics claim that in all cases it can be avoided by supposing that, where it seems to be needed, the poet substituted a trisyllabic foot for a dissyllabic. (Waddy)

4. Ecthlipsis M in th' end hath useless fixt, When vowel or H begins the word that's next. (Holmes)

5. Elision is the running together of two syllables into one by the dropping of one or more letters. This may sometimes by necessary in English verse, but some of our best critics claim that in all cases it can be avoided by supposing that, where it seems to be needed, the poet substituted a trisyllabic foot for a dissyllabic. (Kellog, 239)

1. The second line illustrates the omission of letters from words via ecthlipsis to accommodate the poetical meter of the second line:
Multum ille et terris iactatus et alto
Mult'ill'et terris iactatus et alto
—Mosellanus (Silva Rhetoricae)

3. In the verse-
Blest as| the inmor| tal gods| is he-
we must run the and im of the second foot together, if we would preserve the dissyllabic foot throughout. (Waddy)

4. Si vit' inspicias, for Si vitam inspicias. (Holmes)