Synonyms for Moreover:

adv.

additionally (adverb)
besides, further, what is more, furthermore, likewise, more, as well, in addition, to boot, yet, also, too, by the same token.
also (adverb)
together with, likewise, additionally, not to mention, further, Including, also, And, furthermore, too, in addition, as well as, along with, besides.
however (adverb)
but, however, nevertheless, Albeit, though, although, yet, still.

adv

additionally (adverb)
further.
along (adverb)
as well.
also (adverb)
besides, as well as, not to mention, And, in addition, too, also, together with, along with, furthermore, to boot, additionally, likewise, Including, further.
however (adverb)
but, however, although, though, nevertheless, furthermore, still, Albeit, yet.
to a greater extent (adverb)
more.

n.

essentially, first, mainly, at the end of the day, basically, importantly, the fact (of the matter) is, in essence, not just any..., by the same token. in addition (noun)
increase, more, item, to boot, as well.
moreover (noun)
what is more, furthermore.

Other synonyms:

in addition
more, item.
Other relevant words:
as well, more, to boot, additionally, by the same token, what is more, item.

Usage examples for moreover

  1. Each had a special cup, moreover – A Prisoner in Fairyland by Algernon Blackwood
  2. Moreover he has not got it in him. – The Vultures by Henry Seton Merriman
  3. Moreover she loved me,- too well, indeed, to wish to make me unhappy. – The Marrow of Tradition by Charles W. Chesnutt