Which prefix indicates a meaning of "counter" or "against"?

The prefix that signifies "counter" or "against" is "contra-." This prefix originates from Latin, where it means "against" or "opposite." It is commonly used in medical terminology to describe actions or conditions that oppose or counteract something. For example, in the term "contraceptive," it denotes methods that effectively prevent conception, or pregnancy, which is considered a counteraction to fertilization.

The other prefixes listed have different meanings: "meta-" often indicates a change or transformation; "bi-" refers to two or dual; and "ami-" relates to love or affinity. Thus, the uniqueness of "contra-" in conveying opposition makes it the correct choice.