To increase over a period of time; to accumulate(verb)
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Use "mount up" in a sentence
"I'm waik, but just bye ordinar 'comfortable, awfu' light like, as if I could just mount up on angels 'wings, ye mind, and flee –"
"They mount up as eagles, with ever-renewing strength."
"Replied one of them, ‘O Sa’id, with a run and a spring mount up to yonder niche442 and thou wilt find there a sharpened scymitar of copper: bring it to me and I will tell thee what to do.’"