speechless

As a verb astonish

is surprise, flabbergast.

As an adjective speechless is

not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc.

As adjectives the difference between speechless and false

is that speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc while false is (label) one of two states of a boolean variable; logic.

As adjectives the difference between speechless and undefined

is that speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc while undefined is lacking a definition or value.

Speechless is a related term of still.

As an adjective speechless

is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc.

As a noun still is

.

As adjectives the difference between astounded and speechless

is that astounded is surprised, amazed, astonished or bewildered while speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc.

As adjectives the difference between speechless and shocked

is that speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc while shocked is surprised, startled, confused, or taken aback.

As a verb shocked is

(shock).

As adjectives the difference between stiff and speechless

is that stiff is of an object, rigid, hard to bend, inflexible while speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc.

As a noun stiff

is an average person, usually male, of no particular distinction, skill, or education, often a working stiff or lucky stiff.

As a verb stiff

is to fail to pay that which one owes (implicitly or explicitly) to another, especially by departing hastily.

As adjectives the difference between speechless and breathtaking

is that speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc while breathtaking is stunningly beautiful; amazing.

As adjectives the difference between tightlipped and speechless

is that tightlipped is an alternative spelling of lang=en while speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc.

As adjectives the difference between quiet and speechless

is that quiet is with little or no sound; free from of disturbing noise while speechless is not speaking; not knowing what to say; silent, especially due to surprise, amazement, etc.

As a verb quiet

is to become quiet, silent, still, tranquil, calm.

As a noun quiet

is the absence of sound; quietness.