A cipher is the numeral zero or someone without influence or importance. Don't vote your popular classmate to be the student council leader if he or she is actually a cipher, someone who can't do the job effectively.
Cipher comes from the Arabic sifr meaning "nothing" or "zero" and came to Europe as a word along with the Arabic numeral system. As early codes substituted numerals for letters to hide the wordâ€™s meaning, codes became known as ciphers. If you crack a cipher, you break the code enabling you to understand the message. An encoded message is also called a cipher. Send one to your friend if you don't want anyone to know what you're saying!
Primary Meanings of cipher
1. 
nv 
a secret method of writing
convert ordinary language into code

2. 
n 
a mathematical element that when added to another number yields the same number

3. 
v 
make a mathematical calculation or computation

Full Definitions of cipher
1
n a secret method of writing
 Synonyms:
 cryptograph, cypher, secret code
 Type of:

code
a coding system used for transmitting messages requiring brevity or secrecy
2
n a mathematical element that when added to another number yields the same number
n a quantity of no importance
n a person of no influence
 Types:

pipsqueak, small fry, squirt
someone who is small and insignificant

jackanapes, lightweight, whippersnapper
someone who is unimportant but cheeky and presumptuous
 Type of:

common man, common person, commoner
a person who holds no title
3
v make a mathematical calculation or computation

work out
be calculated
 Types:
 show 40 types...
 hide 40 types...

quantise, quantize
apply quantum theory to; restrict the number of possible values of (a quantity) or states of (a physical entity or system) so that certain variables can assume only certain discrete magnitudes that are integral multiples of a common factor

extract
calculate the root of a number

process
perform mathematical and logical operations on (data) according to programmed instructions in order to obtain the required information

prorate
divide or assess proportionally

miscalculate, misestimate
calculate incorrectly

recalculate
calculate anew

average, average out
compute the average of

factor, factor in, factor out
resolve into factors

add, add together
make an addition by combining numbers

deduct, subtract, take off
make a subtraction

multiply
combine by multiplication

divide, fraction
perform a division

extrapolate, interpolate
estimate the value of

differentiate
calculate a derivative; take the derivative

integrate
calculate the integral of; calculate by integration

survey
plot a map of (land)

approximate, estimate, gauge, guess, judge
judge tentatively or form an estimate of (quantities or time)

budget
make a budget

capitalise, capitalize
compute the present value of a business or an income

resolve, solve
find the solution

square
raise to the second power

cube
raise to the third power

foot, foot up
add a column of numbers

carry back
deduct a loss or an unused credit from taxable income for a prior period

raise
multiply (a number) by itself a specified number of times: 8 is 2 raised to the power 3

halve
divide by two; divide into halves

quarter
divide by four; divide into quarters

triangulate
survey by triangulation

quantise, quantize
approximate (a signal varying continuously in amplitude) by one whose amplitude is restricted to a prescribed set of discrete values

misgauge
gauge something incorrectly or improperly

place, put, set
estimate

give
estimate the duration or outcome of something

lowball, underestimate
make a deliberately low estimate

assess
estimate the value of (property) for taxation

make
calculate as being

count, reckon
take account of

overcapitalise, overcapitalize
estimate the capital value of (a company) at an unreasonably or unlawfully high level

factorise, factorize
resolve (a polynomial) into factors

truncate
approximate by ignoring all terms beyond a chosen one

guesstimate
estimate based on a calculation
 Type of:

reason
think logically