1. (noun) an unknown and unexplored region

• terra incognita
• unknown region

2. (noun) anyone who does not belong in the environment in which they are found

• alien
• stranger

3. (noun) a variable whose values are solutions of an equation

• unknown quantity

4. (adjective) being or having an unknown or unnamed source

• nameless
• unidentified
• unnamed

5. (adjective) not famous or acclaimed

• obscure
• unsung

6. (adjective) not known before

• strange

1. (adjective) not known

• chartless
• uncharted
• unmapped
• little-known
• unbeknown
• unbeknownst
• undiagnosed
• undiscovered
• unexplored
• unheard-of
• unidentified

2. (adjective) being or having an unknown or unnamed source

• anon.
• anonymous

3. (adjective) not known to exist

• unsuspected

4. (adjective) not famous or acclaimed

• inglorious

5. (adjective) not known before

• unfamiliar

1. (noun) anyone who does not belong in the environment in which they are found

• foreigner
• outsider

1. (adjective) not known

• inglorious
• unacknowledged
• unfamiliar

1. (noun) an unknown and unexplored region

• region

2. (noun) anyone who does not belong in the environment in which they are found

• interloper
• intruder
• trespasser

3. (noun) a variable whose values are solutions of an equation

• variable

1. (noun) anyone who does not belong in the environment in which they are found

• acquaintance
• friend

2. (adjective) not known

• known

1. (noun) anyone who does not belong in the environment in which they are found

• alien
• exotic

2. (adjective) not known

• alien
• stranger
• unknown quantity

3. (adjective) being or having an unknown or unnamed source

• anonymity
• namelessness

4. (adjective) not famous or acclaimed

• humbleness
• lowliness
• obscureness
• unimportance
• obscurity

5. (adjective) not known before

• strangeness
• unfamiliarity