WordNet sense 1 (having strength or power greater than average or expected):

strong

WordNet sense 2 (capable of being perceived by the mind or senses):

perceptible

WordNet sense 3 (undesirably noticeable):

obtrusive

WordNet sense 4 (strongly marked; easily noticeable):

marked

WordNet sense 5 (capable of being seen or noticed):

observable

WordNet sense 6 (easily seen or detected):

detectable