an imaginary line between areas, countries, surfaces etc

outer limit

that can be argued about because uncertain

controversial

feeling, causing, doubt

questionable, unclear

a narrow border

border

the last part (of something); the place where (something) stops

extreme, limit

(of a word) having a double or doubtful meaning

doubtful, uncertain

a border of loose threads, e.g. on a rug; an edge (of a crowd, forest etc)

border, trimming

a part of a country bordering on another country; an extreme limit

boundary

a thin long mark on a surface; to attach an inside layer of material to (a bag, box, drawer etc or to clothing)

mark, stroke; border

(of a person, thoughts) confused (e.g. because of alcohol)

doubtful, uncertain

(the instrument of) the outer boundary of a closed figure or area

circumference, border

of, on, forming, a periphery; having only a little importance

minor, outside

uncertain; unsafe; depending on chance

tricky, doubtful

not yet having made up one's mind

not sure, not definite

(of a person, condition) not stable

doubtful

not confident; not certain or reliable

doubtful, insecure

a border (e.g. strip of grass at the side of a road); to be very close to (doing) it; to be almost the kind mentioned

extremity, limit

wavy

doubtful, weak