Mar 9:1 There be some of them that stand here, which shall not taste of death...

Mar 9:1 Verily I say unto you, That there be some of them that stand here, which shall not taste of death, till they have seen the kingdom of God come with power.
Alternative: To tell the truth, there are some of you standing here who shall not taste death until you see clearly that the kingdom of God has finally begun its influence.

This verse is mistakenly seen as a prediction of the end of the world in the lifetime of some of the apostles, but it is often explained as a prediction of the transfiguration, which follows almost immediately in Mark. However, as the alternative translation above indicates, the phrase "kingdom of heaven" and "kingdom of God} is never used to mean our idea of an afterlife in Christ's words and is unlikely to refer to transfiguration (see here for more).

The phrase "come with power" can also mean "start in influence."  The primary meaning of the word translated as "come" is "to start{ though it can be used to mean a motion in any direction. Part of this phrase is used in the Lord's prayer (Mat 6:10) for "your kingdom come," which I usually think of as meaning "your kingdom is beginning" or "your kingdom is under way." Neither here nor in the Lord's Prayer is the "come" in the future tense. Here the tense indicates that it is in the past (it has finished starting) while the tense in the Lord's prayer is indicates that it continues without reference to time (it is starting).

The word translated as "see" means to perceive and experience as well as to physically see. It is often translated in the Gospels as "know."  Here, the meaning is that they will know what they have begun.

It is also interesting here that Christ doesn't say that his followers will die, but merely that they will "taste", "feel," or  "experience" death. The word used means all of these things.  This inference is that this is a bodily experience not an spiritual one, because we experience it.

"Stand" is from histêmi (histemi), which means "to make to stand", "to stand", "to set up", "to bring to a standstill", "to check", "to appoint", "to establish", "to fix by agreement", "to be placed", "to be set", "to stand still", "to stand firm", "to set upright", "to erected", "to arise," and "to place." Like the English words "put" and "set," it has a number of specific meanings from "to put down [in writing]", "to bury", "to establish", "to make", "to cause," and "to assign."

"Taste" is from geuomai (geuomai), which means "to taste", "to feel," and "to experience."

"Death" is thanatos (thanatos), which means "death" and "a death sentence."

"See" is from eidon (eidon), which means "to see", "to perceive", "to behold", "to experience", "to look", "to see mentally", "to examine", "to investigate", "to see with the mind's eye," and "to know how."

"Kingdom" is from basileia (basileia), which means "kingdom", "dominion", "hereditary monarchy", "kingly office," (passive) "being ruled by a king," and "reign."

"God" is from theos (theos), which means "God," the Deity."

"Come" is from erchomai (erchomai), which means to start,"  "to set out", "to come", "to go," and any kind of motion. It means both "to go" on a journey and "to arrive" at a place.

"Power" is from dunamis (dynamis), which means "power", "might", "outward power", "influence", "authority", "elementary force", "faculty", "capacity", "craft", "art", "capable of existing", "capable of acting", "worth," and "value."